Siphona´ceæ.—The structure of this family may be illustrated by the genus Vauchéria, of which two or three species are common on damp ground or in freshwater pools, forming a green layer. At first sight, the filaments of which the little plants consist appear like those of a stout Conferva; but on close examination they are found to be branched, and not jointed, consisting of a single cell from end to end (Pl. VI. fig. 26). The reproduction is effected by the agency of two kinds of organs, antheridia and capsules (sporangia), situated near each other (fig. 26 a) on the walls of the filaments, of which they are protrusions or outgrowths—their cavities being separated from that of the filament by a partition or septum. The antheridia produce spermatozoa, and the sporangia each a spore, the one fertilizing the other in the ordinary manner. In addition to this method of fructification, zoospores are also produced—the ends of the filaments becoming swollen, the contents cut off by a septum, and forming single large zoospores covered with cilia, the further development of which resembles that occurring in the Confervaceæ.

Oscillatoria´ceæ.—The members of this family are commonly found in stagnant water or on shaded damp ground, especially in the cold seasons of the year, forming green strata or masses.

Oscillatoria autumnális (Pl. VI. fig. 1) occurs everywhere upon damp shaded banks of ditches, especially when newly made, forming a greenish-black closely adherent stratum. Under the microscope it is seen to consist of innumerable palish-green filaments; these are jointed or transversely striated, some being straight, others curved, the ends often exhibiting a writhing or worm-like movement. The appearance of these fibres is peculiar, seeming as if they were solid throughout, and so differing from that of the Confervaceæ, in which the cell-walls are readily distinguishable from the cell-contents. The fibres easily break across at the joints; and the last few segments are often narrowed and rounded, so as to form a blunt point. When they have been left in water, they exhibit colourless tubular sheaths surrounding and extending beyond them. These sheaths consist of the consolidated outer portions of the cell-walls; for when the cells undergo transverse division, and expand by growth in the direction of the length of the filament, the original septa or inner walls are broken through, and their remains may often be seen on the inner surface of the sheath, appearing as little teeth.

Oscillatoria nigra (Pl. VI. fig. 2) is another very similar species, forming blackish-green masses, and is common in ditches. It has longer filaments than the last, with narrowed and slightly curved ends; and the endochrome is distinctly granular.

In two other genera of this family, Vib´rio and Spirulína, the filaments are spiral. Vib´rio spiril´lum is excessively minute, colourless, and found in decomposing vegetable mixtures. The short filaments move rapidly through the water, with a corkscrew-like motion. In Spirulína oscillarioídes (Pl. VI. fig. 12), which is more rarely found in clear pond-waters among Confervæ, the filaments are greenish, and form a beautiful simple spiral, resembling that of a very slender spiral vessel.

Lyng´bya murális (Pl. V. fig. 2) is very common on damp walls, gravel walks, &c. It forms a bright grass-green layer, consisting of somewhat rigid curled filaments. The endochrome is usually broader than long; and the cells of the filaments are often found empty, the endochrome having escaped in the form of gonidia.

Pl. VI. fig. 6 represents a species of Bactérium which is not uncommon in decomposing vegetable liquids; the filaments are short, curved, pointed at the ends, and have four joints.

Fig. 26 represents a Schizogónium, found upon damp paths. The filaments resemble those of Lyngbya, but are united in pairs.

Fig. 3 represents a filament of a U´lothrix, which is common in freshwater pools, showing the curious manner in which the endochrome is arranged in the cells, forming bands partially lining the cell-walls.

Nostocha´ceæ.—Two species of the typical genus Nos´toc will serve to represent this family. Nos´toc commúne is found on damp ground or in ponds, and forms to the naked eye firmish, olive-green, skin-like, plaited masses, an inch or more in diameter. Under the microscope it is seen to consist of numerous beaded fibres, imbedded in worm-like gelatinous sheaths; these are curved and interwoven to form the compound mass. In the middle of many of the filaments is an enlarged colourless cell, called the vesicular cell, which is related to the reproduction, but in a manner not yet determined.

Nostoc minutis´simum (Pl. VI. fig. 4) forms solid gelatinous bluish-green masses, varying in size from a pin’s head to a pea; it is found upon unhealthy water-plants kept in glass vessels. The component filaments are very slender, wavy, and the sheaths often have a brownish tinge.

Ulvaceæ.—These Algæ are mostly marine—some, however, being found in brackish or fresh water, or on damp ground, thatch, moss, &c. They are generally of considerable size, forming flat or tubular fronds, often several inches long, a few being filamentous. They consist of one or more sheets or layers of cells, containing mostly green endochrome. This at first fills the cells, but subsequently becomes converted into single spores, or subdivided into numerous ciliated zoospores.

Ul´va latis´sima is very common on the sea-coast, being found attached to stones, shells, &c. It forms a broad, flat, green, rounded or oblong, thin frond, wavy and crumpled at the margins, and from 6 to 18 inches in length. The minute cells form two layers, adherent to each other. The zoospores formed are numerous in each cell.

Enteromor´pha compres´sa (Pl. IV. fig. 31) is also common in the sea and in brackish ditches; it is often found floating. The frond is green, tubular, flattened or compressed, and branched, the branches being usually simple and narrowed at the base. The frond consists of two layers of minute cells, separated by a space rendering it hollow. The zoospores are numerous in the cells (fig. 32).

Palmella´ceæ.—These Algæ are found in fresh or salt water, or on damp earth, wood, &c. They are green or red, forming round or irregular masses or strata. They consist of loosely connected cells, imbedded in a gelatinous mass or matrix, thus forming a frond.

Chlorococ´cum vulgáre (Pl. II. fig. 1) is very common upon the bark of elm-trees, palings, &c., forming a green granular crust. It consists of minute rounded or oval cells, mostly undergoing division into twos, fours, or eights. These cells are attached to the sides or ends of very fine colourless filaments. It is most probable that this organism, which is usually placed among the Algæ, consists of the gonidia of a Lichen.

Chlorococcum muror´um forms a somewhat similar but soft and thin green layer, upon damp walls or other porous bodies. It consists of very minute oval green cells, with thick walls, and imbedded in the ends of prolongations of a gelatinous matrix.

Palmel´la cruen´ta (Pl. VI. fig. 25) forms a portwine-red layer at the bottom of damp walls or on the ground. It is composed of pale red cells, imbedded in no definite order in a colourless gelatinous matrix. The cells are filled with red granules, and are often found undergoing division.

Pl. VI. fig. 19 represents a species of Glœocap´sa, in which the cell-envelopes do not soften and unite to form a gelatinous matrix, as in Palmella and other members of the family, but are persistent. This species occurs in fresh water containing Confervæ.

Chara´ceæ.—This family consists of the single genus Chára, the systematic position of which is not agreed upon by authors; as however its structure will be better understood after what has been gone over, it may be conveniently considered here.

There are several species of Chara, the one illustrated, Chara vulgáris (Pl. VI. fig. 21), being commonly found in ditches and pools. It consists of long main stems, often a foot in length, which are branched, and surrounded at tolerably regular intervals by whorls of branchlets. In some species, the stems and branches consist simply of elongated cells, arranged end to end; while in others, of which Chara vulgaris is one, the central cells are surrounded by a number of narrower spirally arranged cells, forming an outer coating.

The Charæ have long formed interesting microscopic objects, on account of the circulation of the protoplasm being visible in the cells, as in the hairs of Tradescantia. This is best seen in those species in which the outer layer of cells is absent from the stems, and which were formerly arranged in a separate genus (Nitella). But it may also be seen in the stems and especially the young branchlets of any of the other species; and as the granules of the protoplasm are large, the phenomenon is more easily witnessed than in Tradescantia.

The fructification consists of two kinds of organs, viz. red globules (Pl. VI. fig. 22) representing the anther-organ, and green capsules (fig. 22), or nucules, corresponding to the ovaries. The structure of the globules is very curious. Their transparent walls (fig. 20) consist of eight somewhat triangular plates, each of which is composed of cells radiating from a centre; and from the inside of each of these centres arises a tubular cell extending to the middle of the globule, the unattached ends giving origin to numerous colourless coiled filaments, consisting of minute cells arranged end to end, each containing a very minute coiled spiral fibre, to which are attached two exceedingly slender cilia. These ciliated fibres are the spermatozoa. The capsules or nucules (fig. 22), which are situated near the globules, are urn-shaped, coated with spiral cells, and crowned with five shorter cells. When the globules are ripe, they become ruptured by the separation of the valves; and the spermatozoa, escaping from the cells of the coiled filaments, swim about and enter a canal in the capsules to fertilize the ovule contained within.

The Charæ grow readily in a glass jar of fresh water, with a few pebbles at the bottom; and if the plants be not overgrown with Confervoids, the fructification will continue to be produced almost throughout the year.

The circulation is best seen in the whorled branchlets, a portion of the growing ends being placed in a live-box, or simply laid upon a slide in water and covered with thin glass.

Preservation.—The Algæ are best preserved in two ways,—the entire fronds being dried upon paper under pressure, as directed for the Ferns; and small portions, showing the minuter structures and fructification, being mounted in chloride of calcium or glycerine. If it is required to preserve the marine Algæ according to the first method, they should first be immersed for a time in fresh water, to dissolve out the saline matters derived from the sea-water, which would keep them damp and ultimately spoil them. After these matters have been removed, the fresh water should be changed, and pieces of paper placed beneath them while suspended in the water; on withdrawing the paper carefully, keeping the Algæ at the same time spread out, they may be made to retain the required position; and when the water has drained away, and the remaining moisture has mostly evaporated, they may be submitted to pressure in a press.

The Confervoid Algæ may be conveniently spread out upon paper and preserved in the same manner, as some of the distinguishing characters are founded upon their appearance in the dry state, their adhesion to the paper, &c. Moreover they can then at any time be minutely examined, by the immersion of a small portion in water.

CHAPTER VIII.

LICHENS.

The structure of the Lichens is simple, no distinction of root, stem, and leaves existing in them, although certain dry root-like fibres exist in many of them, by which the plant is fixed to the matrix. The whole consists mainly of a frond or thal´lus (θαλλὀς, a leaf). This is either raised above the surface of the matrix in a shrubby form, or spread upon the surface as a flexible lobed layer (Pl. II. fig. 2), or it is dry and brittle (crustaceous) and closely adherent (Pl. II. fig. 26).

The fructification consists of little saucers, disks, or streak-like furrows, often of a different colour from the thallus, the structure of which will be best illustrated by reference to a few common species.

Parmelia´ceæ.—Parmélia parietína (Pl. II. fig. 2) is a very common Lichen, found on the bark of trees, on old palings, &c. It is of an orange-yellow colour, the thallus being flat, lobed, and scalloped (crenate) at the margins. The structure of the thallus may serve to represent that of most of the Lichens. It consists of three layers,—an upper cortical or epidermic layer, which is continued over the margins to the under surface of the thallus, to form the under layer; and between these is the middle or medullary layer. The medullary layer consists of interwoven fibres, which are more closely packed towards the upper and under surfaces, so as to give them a cellular appearance. Near the upper part of the medullary layer, a number of minute rounded green cells exist, lying loosely in its meshes (Pl. II. fig. 4 a). These green cells (gonidia) appear to correspond to the buds of the higher plants, and, when detached from the plants, they are capable of growing into new individuals.

On the upper surface of the thallus of Parmelia (fig. 2) the fructification may be observed. This consists of saucers or shields (apothécia, ἁποθἡκη, a repository), formed of a raised and expanded portion of the thallus (fig. 3), and containing the spores. The spores are enclosed in closely set upright cells, or spore-sacs (figs. 4 b and 5 b), called as´ci (ἁσκὀς, a bottle) or thecæ; and intermingled with the asci are filaments, enlarged and coloured at the ends (paraphyses), which are probably abortive asci.

In systematic works upon the Lichens, the saucers and their contents are included in the term apothecia, the saucer alone being called the excip´ulum (excipulum, a receiver); the mass of asci and paraphyses forming the nucleus or thalámium (θἁλαμος, a bed).

The yellow spores are very minute, each ascus containing eight of them, and they are divided by a transverse partition or septum.

Near the margins of the lobes of the thallus are small dark points. These are the pouting mouths of little capsules (spermogonia) sunk in the substance of the thallus, and containing numerous filaments, terminated by very minute stick-shaped bodies (spermatia), which break off and escape through the orifices of the capsules. These are probably the representatives of the anthers of flowering plants and of the antheridia of the ferns. They are, however, so difficult to find and examine, that I must refer to the Dictionary for a further description and figures of them.

Lecidin´eæ.—This family contains the genus Cladónia, three or four species of which are common on boggy heaths, banks, &c., viz. Cladonia coccif´era, the Scarlet Cup-moss (Pl. II. fig. 21); C. pyxidáta, the Common Cup-moss (Pl. II. fig. 23); C. vermiculáris (Pl. II. fig. 22); and C. rangiferína, the Reindeer Moss (Pl. II. fig. 24). The thallus of these Lichens forms little rounded irregularly overlapping scales, with scalloped edges, overgrowing the surface upon which the Lichens are found. The fruit-stalks, or podétia (ποῦς, a foot), are hollow (fistulose), and either simple and dilated into cups (Pl. II. fig. 23), or branched with the corners or angles between the adjacent branches perforated. The apothecia in the young state resemble those of Parmelia on a small scale; but as they approach maturity, the centre becomes pushed up, so that the spore-layer is extended over the ends of the stalks. In C. coccifera and pyxidata the cups are proliferous at the margin; i. e., branches upon which the apothecia are placed arise from it. The asci and paraphyses are very minute, but do not differ essentially in structure from those of Parmelia. In C. vermicularis the podetia are pointed and more solid than in the other species, the apothecia forming very minute spots at their apices.

Graphid´eæ.—To this family belong Gráphis scripta (Pl. II. fig. 26) and Opeg´rapha betulína (Pl. II. fig. 30). These little Lichens are easily overlooked, from the thin and but slightly raised thallus being only visible to the naked eye as a discoloration of the bark of the trees upon which they grow; while the fructification is very minute, forming little black streaks or lirel´læ (lira, a furrow), irregularly arranged, and resembling somewhat the letters of some of the Oriental alphabets.

In Graphis scripta (fig. 26) the thallus is thin, somewhat membranous, smoothish, shining, greyish white, and faintly bordered with black. The lirellæ (fig. 27) are partly sunk in the bark, winding and narrow, some being simple, others branched; and they are surrounded by a raised border, formed by the thallus. The lirellæ are lined at the sides with a black (carbonaceous) layer or excip´ulum, within which are situated the asci and paraphyses. The spores (Pl. II. fig. 29) are 8-cleft, the segments being again divided longitudinally into little spores or sporidia.

In Opegrapha betulina (Pl. II. fig. 30), which is found on the bark of the birch-tree, the thallus is thin, dirty yellowish white, bordered with black. The lirellæ (figs. 31, 32) are mostly simple, without a raised border of the thallus, and the excipulum forms a complete lining to them. The spores (fig. 33 a) are 3-cleft, and taper at the ends.

Calici´eæ.—Calic´ium clavel´lum (Pl. II. fig. 6) is a pretty little Lichen, growing upon old boards and farm-buildings. The thallus is granular and greyish white. The apothecia (fig. 7) are stalked and black, but of a lighter colour than the mass of spores forming the nucleus. The spores are very minute, black, oblong, and divided by a transverse septum.

The Lichens are divided into two Orders, according to whether the apothecia are open before the spores are ripe, as in the species noticed above, or whether the apothecia only open to discharge the ripe spores. The first Order forms the Gymnocar´pi (γυμνὀς, naked, καρπὀς, fruit); the second forms the Angiocar´pi (ἁγγεῖον, vessel, capsule).

Preservation.—The Lichens are readily preserved, on account of their dry nature; they need simply be kept in a dry place, and glued to pieces of card. If room is an object, they may be dried under pressure, as in the case of the flowering plants. When re-moistened, the minute structures may be easily made out by sections. The smaller ones may be mounted dry, in cells made of the wax cement (p. 16). The minute structures keep well in chloride of calcium or glycerine.

CHAPTER IX.

FUNGI.

Fungi exhibit no separation of root, stem, or leaves, as exists in the higher plants; nor do they contain chlorophyll, the presence of which is so generally associated with the idea of a plant. But they consist of aggregations of mostly elongate cells, forming branched and interlacing colourless fibres, buried like roots in the substance (matrix) upon which they grow, and from which they derive their nourishment; this portion of the Fungus is called the mycélium (μὑκης, a fungus). The portion of the Fungus projecting beyond the surface of the matrix is the fructification; and this is the part usually called the fungus, the mycelium being overlooked by a casual observer. So that here we have a character distinguishing the Fungi from the Lichens, which derive their nourishment from the air, and not from the matrix. The absence of the green cells, or gonidia, forms another character by which the nearly allied members of this class of plants can be distinguished.

The fructification of the Fungi occurs in two distinct forms, in one of which the seeds or spores are naked, and situated at the ends of slender cells or filaments, whilst in the other the spores are contained in usually flask-like cells, called asci, similar to those occurring in the Lichens. In a few Fungi, antheridial organs, called spermogonia, as in the case of the Lichens, have also been detected. The Fungi are divided into six Orders, from each of which a few species may be selected to illustrate their structure more in detail.

Hymenomyce´tes (ὑμἠν, membrane, μὑκης, fungus). This is the highest Order of Fungi, containing a large number of genera and species; as examples of which may be mentioned the common Mushroom, Toadstools, &c.

Their general structure may be illustrated by the examination of the common Mushroom (Agar´icus campes´tris); the species figured (Pl. VII. fig. 1), however, being Agaricus micáceus, which is common at the root of trees, the bottom of decaying posts, &c.

The vegetative part of the fungus consists of a cotton-like mycelium, which is composed of slender, colourless, interwoven filaments, popularly known as the spawn. The portion commonly called the mushroom corresponds to the fructification, and consists of certain parts visible to the naked eye. These are an expanded portion at the top, forming a hemispherical cap, receptacle, or píleus (pileus, a cap), and a stalk, or stípes, upon which the cap is supported. On the under surface of the cap are a number of nearly parallel, radiating, dark-coloured plates or gills, somewhat resembling the gill-plates of a fish. The dark colour of the gills arises from the presence of the spores, which are coloured, although in some species they are white. The surface of the gills, upon which the spores are situated, is called the hyménium (ὑμἠν, membrane). The spores (Pl. VII. fig. 2 a) are microscopic and very minute, and are situated at the ends of little stalks or points (Pl. VII. fig. 2 b), called sterig´mata (στἡρυγμα, a prop), which are four in number, and consist of prolongations of the colourless cells of the hymenium; and these cells are the basid´ia (βασἱδιον, a little base). The detection of the basidia requires great care, as they are very minute and transparent; the best way to observe them is to cut a very small portion from the uninjured edge of one of the gills with a fine pair of scissors, and to examine it in water. If the gills have been bruised, the spores are easily rubbed off, and their connexion with the basidia destroyed.

In the young state of the Mushroom, the fructification appears as little knobs upon the spawn or mycelium. Upon cutting these through perpendicularly, the cap and stalk are found to be enclosed in a skin or wrapper, called the vol´va (volva, a wrapper), and the margin of the cap is continuous with the surface of the stalk, the connecting membrane forming the veil, or vélum (velum, a veil). As the Fungus grows, the cap rises and bursts the volva, which withers and disappears; and the veil is torn through, the portion remaining in connexion with the stalk encircling it as a collar or ring (an´nulus).

Merúlius lach´rymans, the Dry-rot Fungus, which belongs to the same family (Agaricíni) as the Mushroom, deserves notice from its very destructive action upon decaying timber. The filaments of the mycelium may readily be detected in the rotting wood by examining a thin section in water. The receptacle forms a yellowish-orange or brownish flattened mass, some inches in breadth, with white downy margins; and the surface exhibits folds arranged so as to form large irregular pores, instead of gills as in the Mushroom.

In other families the cap and stalk appear fused together and undistinguishable; or the fructification assumes the form of the cap or the stalk only, and the hymenium does not form gills. Thus in the family Polyporei (the members of which are common on the trunks of trees and on rotten posts, and some of which are very large) the basidia are situated upon the inner surface of tubes immersed in the under part of the mass, their orifices forming minute pores, yet visible to the naked eye. In other families the basidia are placed upon the outer surface of a club-shaped or branched receptacle (Clavarini), or upon external prickle-like points (Hydnei), &c.

In the family Tremellini the receptacle forms a gelatinous mass, and the basidia are situated upon its surface, terminating the filaments of which it is composed. One species, Dacrymy´ces stillátus, is very common on fir posts in the winter and spring, forming little roundish, yellowish-orange, cushion-like masses.

Gasteromyce´tes (γαστἠρ, belly, hollow, μὑκης, fungus).—This order of Fungi, which contains the Puff-balls and many others not readily procured, must be very briefly noticed. The spores are contained in a capsule or perid´ium (πηρἱδιον, a little bag) which is often of large size, and are situated upon a hymenium forming folds, partitions (septa), or a lattice-work.

A small species, Physárum album (Pl. VII. fig. 3), is often found growing upon rotten stems of plants and decaying sticks. The capsules are minute, grey, brittle, and black within, from the presence of the spores (fig. 4), which are lens-shaped, and arise from the ends of short filaments.

Coniomyce´tes (κὁνις, dust, μὑκης, fungus).—This Order contains some beautiful microscopic Fungi, several of which are very common. Many of them grow upon living plants, while others are found upon decaying stems, sticks, &c. The mycelium consists of inconspicuous, fine filaments, which run beneath the epidermis and bark of leaves and stems, or exist in the intercellular passages, the fruit bursting through the surface. The spores are short-stalked, forming sty´lospores (στῦλος, stalk, σπὁρος, seed) or conid´ia (κονἱδιον, little dust). But there is great confusion in the descriptions of the spores of the same Fungus by different botanical authors, some describing the fruit (in Pl. VII. fig. 15, for instance) as composed of rows of spores, while others regard it as forming a single septate (septum, a partition) or partitioned spore.

Tor´ula herbárum (Pl. VII. fig. 12) is very common on the decaying stems of plants, especially those belonging to the Parsley order (Umbelliferæ), forming greenish-black streaks or patches. The spores (fig. 13) are grouped into chains or beaded (moniliform) rows, with very short stalks, and these are crowded to form the black patches visible to the naked eye. Under the microscope the spores appear of a brown colour.

Torula cásei (Pl. VII. fig. 11) forms reddish or white patches upon decaying cheese. It consists of branched, interwoven, tufted filaments (flocci), with comparatively large spherical spores arranged in rows at their ends.

Nemas´pora crócea (Pl. VII. fig. 10) is a very curious member of this Order, and is found upon decaying beech-sticks. It appears as an orange-coloured tendril-like gelatinous mass of spores, bursting through a little pore on the surface of the bark. The spores (fig. 10 a) are very minute, slender, and curved, and under a high power appear jointed.

Æcid´ium grossuláriæ (Pl. VII. fig. 8) is found very commonly on the leaves of the gooseberry-bush. It forms to the naked eye oval or rounded spots (sori), of a red colour; and on close examination, the spots appear dotted with yellow points. Each point is the orifice of an open capsule (peridium), which has burst through the epidermis of the leaf (Pl. VII. fig. 9 p). The capsules are split or lacerated at the margins, and form little cups containing the spores. The spores are very minute, yellow, and are arranged in closely packed moniliform rows. The red colour depends upon the altered chlorophyll of the leaf. On the leaves containing the spore-capsules or peridia will be found smaller, brownish-yellow capsules (spermogonia) partly imbedded in their substance (Pl. VII. fig. 9 s). These contain minute filaments (sterigmata), terminated by short rows of rounded cells (spermatia), which are supposed to exert an antheridial function. The species of Æcidium are very numerous, and many of them are extremely common—as those upon the nettle, the barberry, the dandelion, the wood-anemone, the violet, and buttercups. The groups of capsules form exquisite opake objects under a low power of the microscope.

Phragmid´ium bulbósum (Pl. VII. fig. 14) is another very beautiful coniomycetous Fungus. It forms little reddish, afterwards sooty dots upon the under surface of the leaves of various species of Bramble (Rúbus). The oblong spores (fig. 15) are from 2-to 4-septate, and stalked, the stalks being swollen or bulbous at the base. The spores, which appear brown when magnified, are covered with little knobs (tuberculate) on the surface; and the uppermost little spore or sporidium is terminated by a minute point (apiculate). Among the spores are numerous barren filaments or paraphyses.

Puccin´ia gram´inis (Pl. VII. fig. 16) is to be found everywhere upon damp rotting straw, and upon grasses. It forms sooty irregular streaks, consisting of densely crowded, one-partitioned (uniseptate) spores (fig. 17), which appear brown under the microscope. This Fungus is sometimes called “mildew.” There are numerous other species of Puccinia which occur upon common plants.

Urédo seg´etum is the “smut” of wheat, barley, and oats—a fungus too well known to the farmer. It forms sooty masses, bursting through the epidermis of the stalk and ears of the corn, and soiling the fingers when handled. The spores (Pl. VII. fig. 5) are exceedingly minute, and the stalks are so slender and loosely connected with them that they are not readily detected. Under the microscope the spores appear brown and faintly dotted, this appearance arising from a reticulated structure of the surface, similar to that of the poppy-seed on a very small scale.

Urédo cáries is the “bunt” of corn. It grows within the grain, filling it with a sooty, fœtid mass. The spores (Pl. VII. fig. 6) are considerably larger than those of the last species, and their surface is distinctly reticulated. They are attached to the filaments of the mycelium, as in Uredo segetum.

The spores of both these species of Uredo may be found in most kinds of flour and bread, especially in those of inferior quality.

Urédo can´dida (Pl. VII. fig. 7) is another species, forming white dots upon the leaves of the common Shepherd’s Purse (Capsel´la bur´sa pastor´is)—which is easily recognized by the form and arrangement of the pods (fig. 19). The spores (s) are rather large and white.

Other species of Uredo are very common upon numerous species of weeds or wild flowering plants; and they so closely resemble each other that, when one is known, the others are easily recognized. Usually each species occurs upon a distinct species of plant, as is the case with parasites generally. In many of them the spots (sori) exhibit a thin membrane covering the spores, which bursts down the middle, so as to bear some resemblance to a capsule. But there is no true capsule, the membrane consisting of the epidermis of the leaf or stalk of the plant, which is raised and torn by the expansion of the growing fungus; so that the peridium is spurious, as belonging to the matrix, and not to the fungus. It may be mentioned here that the so-called species of Uredo are not truly distinct species, but are the forms of species of Puccinia, Phragmidium, &c.; so that the latter genera have two kinds of fruit, one of which is a Uredo, the other a Puccinia. But I must refer to the Dictionary for further details upon this point.

Hyphomyce´tes (ὑφἁω, to weave, μὑκης, fungus). In this, the 4th Order of Fungi, are contained many of the commonest moulds which are found growing upon decaying substances, and sometimes upon living plants. The mycelium creeps among the particles of the substance, or the elements of the tissues, upon which the Fungus lives, in the form of slender threads or filaments. The spores, which are either simple or partitioned (septate), and naked, occur either singly or in rows at the ends of fine interwoven cottony threads or floc´ci (floc´cus, a flock of wool), which are generally very evident to the naked eye. The threads supporting the spores form the ped´icels (pedicel´lus, a little foot). In technical descriptions, these filaments, which are usually composed of cells arranged end to end, are said to be septate (Pl. VII. fig. 26), and not jointed, as in the case of the filaments of the Confervæ, which are constructed in a similar manner. When not septate, the filaments are said to be continuous.

Stilba´cei.—To this family belongs Tuberculária vulgaris (Pl. VII. fig. 28), which is found upon decaying sticks and branches of trees, especially the lime-tree. It forms little firm red knobs or tubercles, each of which is a receptacle. On making a section of a receptacle (Pl. VII. fig. 29), the interior is seen to be paler than the bright red surface, and a short broad stalk comes into view. The receptacle is composed of crowded cell-filaments, so short near the base as rather to resemble cellular tissue (fig. 30); but towards the surface the filaments become extremely slender and branched; and each branch is terminated by a minute oblong spore, or a short row of them (fig. 31).

If a stick with this Fungus upon it be kept for some time in a damp place, short whitish fibres, branched at the ends, and visible to the naked eye, will be seen sprouting from around the base of the receptacle (Pl. VIII. fig. 1). These, when examined under the microscope, appear composed of fine filaments (Pl. VIII. fig. 2), resembling those of Tubercularia, and having the minute spores at the ends. After a considerable time, the entire receptacle of the Tubercularia becomes resolved into these fibres. In this state the Fungus assumes the characters of an Isária, a genus of a different family of Fungi (Isariacei), so that we have here an Isaria-form of Tubercularia.

Sometimes the tubercles of the Tubercularia become darker, almost black, harder, and granular on the surface. On making a section of them in this state, the whole of the under portion of the surface is found to contain little roundish capsules, containing asci and spores, and it constitutes Sphæ´ria fragifor´mis (Pl. VII. fig. 32). As the Sphæria is the more complex and highly organized condition of this Fungus, the other two conditions must be regarded as forms, and not as species of separate genera.

Dematie´i.—In this family the filaments upon which the spores are placed are not compacted as in Tubercularia, but separate; and they are of a dark brown or black colour.

Sporoc´ybe alternáta (Pl. VII. fig. 18) is occasionally found upon decaying vegetable substances, forming little black velvety spots or patches. The mycelial filaments are exceedingly minute, septate, tapering at the ends, and terminated by a little tuft of pear-shaped cells, from which the black simple spores arise singly.