A handbook of systematic botany

Order 3. Cannaceæ. American herbs without aromatic properties. Flowers asymmetric (Fig. 316). Calyx polysepalous. The stamens are petaloid (Fig. 316 st) and barren with the exception of one (the posterior), which bears on one of its edges a bilocular anther; another, which is especially large and coloured, is termed the labellum. The style is compressed and leaf-like, with a small stigma at the apex. Ovules numerous in the 3 loculi. The capsule is furnished with warts or soft prickles. Embryo straight.

Canna (30 species; Trop. Am.). The inflorescence is a terminal spike with 2-flowered unipared scorpioid cymes in the axils of the floral-leaves. Ornamental plants: Canna indica, etc.

The diagram of the andrœcium of the Cannaceæ and Marantaceæ may be represented in the following manner (calyx, corolla and gynœceum being omitted):—

Order 4. Marantaceæ. The flower is asymmetrical. Only 1 or 2 of the 3 stamens in the outer whorl are present as staminodes; in the inner whorl 2 are petaloid and of the sixth stamen one-half is developed as a staminode and the other half bears a bilocular anther. One ovule only in each loculus. The style is strongly curved and at first enclosed in one of the staminodes (hood) of the inner whorl; later on it springs elastically forward towards the other staminode (inner-wing) of the same whorl. The stigma is very oblique or 2-lipped. Two of the three loculi of the ovary, in some (Maranta, Thalia) become small and empty. Embryo curved. Leaves in two rows, with sheath, stalk, and blade (Fig. 317); at the base of the last is a characteristic swelling (articulus).—Phrynium, Calathea, Stromanthe, Ctenanthe, Saranthe, etc. About 150 species; tropical, especially America. The starch of the rhizome of Maranta arundinacea is OFFICINAL, “West Indian Arrowroot.”

Family 7. Gynandræ.

The flowers are hermaphrodite and constructed on the ordinary 3-merous, pentacyclic type with petaloid, epigynous, strongly zygomorphic perianth, and generally one-stamened by the suppression of the other 5 stamens. The family has derived its name from the fact that the stamen is united with the style into a “stylar column” (except Burmanniaceæ). All are herbs; many grow as epiphytes on other plants.

Order 1. Burmanniaceæ. This order forms a transitional link between the Gynandræ and the epigynous Liliifloræ (Amaryllidaceæ), in having a 6-leaved perianth, and 6–8 stamens; but some have a labiate perianth (the median perianth-leaf of the outer whorl being very large). The ovary is most frequently unilocular with three parietal placentæ; but in some it is 3-locular with axile placentation. Capsule. Seeds ∞, small, with endosperm. The relationship to the Orchidaceæ is shown especially in the very imperfectly developed embryo and in the ovary. Small, tropical herbs (59 species); some are saprophytes.

Order 2. Orchidaceæ. The epigynous, petaloid perianth is strongly zygomorphic in having the posterior leaf of the interior whorl, the lip (labellum), differing from all the other leaves in form, size, and colour (except Apostasieæ); the position of the labellum is very frequently reversed, being turned forwards and downwards by the twisting of the ovary (Fig. 318 A). Only 1 of the stamens—the anterior of the external whorl—is developed and bears an anther (by the twisting of the ovary it is turned posteriorly and upwards); the others are entirely wanting (indicated by * in Fig. 318 A) or present as staminodes (Fig. 318 A, δ δ) (except Apostasieæ, Cypripedileæ); the filaments are united with the style to form a column (Fig. 318 B), the stylar-column[30] (gynostemium), and the anther (a) is thus placed on its apex and exactly behind or over the stigma (s). The anther is 4-locular; the pollen-grains do not separate (except Apostasieæ, Cypripedileæ) but remain united either in tetrads or in masses, which correspond to a pollen-mother-cell (Fig. 320 C, D, E); or the pollen-grains, formed in each of the two anther-halves, remain united and form one or a few wax-like masses (pollen-masses, pollinia). The 3 carpels form a unilocular ovary with 3 parietal, deeply bifid placentæ (except Apostasieæ, Selenipedilum). Only the two lateral carpels are prolonged and developed into the stigma (Fig. 318 B, s), while the one lying in the median line, which is situated just within the anther (Fig. 318 A), becomes either rudimentary or developed into the “rostellum” (“a small beak”), on which the sticky bodies (glandulæ) arise; by aid of these the heavy, connected pollen-masses may be glued to the insects which visit the flower, and pollination is thus secured (in Apostasieæ and Cypripedileæ the 3 carpels each contribute to the formation of the stigma). The fruit is a capsule which most often dehisces by 6 valves, 3 of which are broader and bear the placentæ, and 3 alternating with them are narrower and barren (except Vanilla). The very numerous and exceedingly small seeds have no endosperm, and have a somewhat spherical embryo without any trace of external organs. The testa is membranous and loose.

The Orchids are all perennial herbs with diverse habits and varying morphological structure (see the genera); the leaves are scattered, of the usual Liliaceous form, and the inflorescences in all cases are racemes or spikes (sometimes branched), with subtending bracts, but without bracteoles.

The forms which are the least modified are described first.

1. Apostasieæ. The perianth-leaves are almost alike and free. The column is straight, with 3 equally-developed stigmas. Neuwiedia has 3 perfect stamens (1 median of the outer whorl, and 2 lateral of the inner whorl); Apostasia has only 2 perfect (inner lateral) and one barren (the median of the outer whorl), which however may be entirely wanting. The 3 posterior stamens are entirely suppressed. The pollen is powdery. The ovary is 3-locular with axile placenta. 7 species (Tropical East India, Australia).

2. Cypripedileæ.[31] The flower is strongly zygomorphic with a large boat-shaped labellum. There are two perfect stamens belonging to the inner whorl, and the median anterior (later on the posterior) stamen of the outer whorl is transformed into a large, barren, shield-shaped body (Fig. 319). Selenipedilum has a 3-locular ovary, but Cypripedilum (Ladies’-slipper) has a unilocular ovary with 3 parietal placentæ—the typical structure for the Orchids. The pollen-grains are separate (not in tetrads) and all the 3 lobes of the stigma are constructed to receive them. This group is therefore, next to the Apostasieæ, the least modified among the Orchids; in all the following groups, one of the lobes of the stigma is differently developed from the others, and there is only one stamen.—Terrestial Orchids.—The pollination of C. calceolus is effected by the forcible entrance of insects into the boat-shaped labellum (Fig. 319 p’) at i, and their escape at ex (in 2) where the anthers are situated; in this way the stigmas will first be touched and then the anthers. The pollen-grains are surrounded by a sticky mass in order that they may adhere to the insects.

3. Neottieæ. The majority are terrestrial Orchids with creeping, sympodial rhizomes; the blades of the leaves are not detached from the stem at joints, and have convolute vernation. The anthers do not drop off, but persist in the withered condition; their apex is brought in contact with the rostellum (acrotonous Orchids). The pollen-grains are united in tetrads, which, however, often hang loosely together in pollinia, attached to a sticky part of the rostellum (“adhesive disc”), so that they adhere to the insects, and are by them transferred to the stigmas. Spiranthes. Listera; Neottia. N. nidus-avis (Bird’s-nest) is brown (it has little chlorophyll) in colour, has no foliage-leaves, and lives mainly as a saprophyte; the rhizome is studded with unbranched, fleshy roots which may form buds at their extremities.—Vanilla climbs by aerial roots. The fruit is fleshy and hardly opens, or does so irregularly.—Epipactis, Cephalanthera.—Epipogon and Limodorum are saprophytes without chlorophyll.

4. Ophrydeæ. Anthers 2-locular, not falling off, on a very short column. The anther is united at its base with the rostellum (basitonous Orchids, Fig. 320 A, B), while in all other Orchids it is connected at the apex (acrotonous Orchids). The pollen-grains in each loculus are united into small “masses” (massulæ), each of which corresponds to a pollen-mother-cell in the anther, and which hang together by elastic threads (Fig. 320 C, E). Each pollinium is attached at the base by a stalk (caudicle) to an adhesive disc, formed by the modified stigma (rostellum), and is easily liberated from it (Fig. 320 C, D, F). The pollinium, which is formed in an anther-loculus, together with its caudicle and adhesive disc, is termed “pollinarium” (Fig. 320 C).—All Ophrydeæ are terrestrial with tuberous roots, two of which are present in the flowering period, an older one (from the preceding year) containing the nourishment for the flowering-shoot of the year, and a young one which is intended to contain the reserve material for the following year. Inflorescence terminal.

Orchis. The lip has a spur; each of the club-like pollinia is attached to its own adhesive disc, the discs being enclosed in a common pouch formed by the rostellum (Fig. 320 C, D). Tubers ovate, undivided: O. morio, mascula; tubers palmate: O. incarnata, maculata, majalis.—Ophrys; no spur, the two adhesive discs are each enclosed in a separate pouch (Fig. 320 F).—Anacamptis and Serapias have one adhesive disc.—Habenaria, Gymnadenia, Platanthera, Herminium, Nigritella, Cœloglossum, etc., have naked adhesive discs (no rostellum).

Class II. Dicotyledones.

In this class THE EMBRYO has 2 seed-leaves, a rule from which there are few exceptions (e.g. Ficaria, Cyclamen, Pinguicula, certain species of Corydalis, with only 1; and a few, mostly parasitic forms, e.g. Monotropa, Orobanche, Pyrola, entirely without cotyledons). On germination the cotyledons nearly always raise themselves above the ground as green, assimilating leaves and are then termed aerial or epigean, in contradistinction to the underground or hypogean which are always buried. The structure of the seed varies (endospermous or exendospermous); the embryo may be straight or curved. In many instances the primary root grows as a vigorous tap-root, with weaker branches arising acropetally (in annuals, biennials, many perennials, especially woody plants); but in a large number of herbaceous perennials, which have rhizomes, the root behaves very much as in the Monocotyledons. The roots generally increase in thickness by means of a cambium.

The stem, when seen in transverse section, has its vascular bundles arranged in a ring; in reality, however, they form a kind of cylindrical network in the stem; the bundles are open, and thickening takes place by means of a cambium; annual rings are formed in the perennial stems. There is a rich and very varied form of branching. The two first leaves of a shoot (fore-leaves) are placed nearly always to the right and to the left; the same arrangement is found in the two first leaves developed on the flower-stalk, and these are, as a rule, the only two; they are found below the calyx and are usually termed the “bracteoles.” It has become customary to indicate the bracteoles by the letters α and β, according to their sequence of growth, and in that sense these letters will be employed in the following diagrams.

The arrangement of the leaves varies very much; there is also a great variety of shapes in the leaves and their venation, but the linear leaves, with parallel venation, so frequent in the Monocotyledons, are seldom met with, as also the large sheaths (though the sheath is well developed in the Umbelliferous plants); stipules occur much more frequently.

The flower is most commonly cyclic, but acyclic or hemicyclic forms also occur. The type which may be taken as a basis consists in the majority of instances, as in the Monocotyledons, of 5 whorls, of which the 4 outer ones (calyx, corolla, and the 2 whorls of stamens) are most frequently 4 or 5 in number and placed in regular alternation, whilst the innermost one (the carpels) has generally fewer members, probably on account of space (Figs. 360, 361, 421, 429, 487, etc.). Trimerous (Figs. 384, 387, etc.) flowers, or those in which the members of the flower are in threes or a multiple of three, also occur, as well as dimerous flowers; other numbers are rare. It is of the greatest importance in connection with the relative position of the members of the flower to the axis and bract (orientation), whether the bracteoles are typically present (even though they may not be developed), or are typically absent. If there are 2 bracteoles present, then their position in a pentamerous flower is often as follows: the first sepal turns obliquely forward, the second is posterior and median, the third obliquely forward, the fourth and fifth obliquely backward; quincuncial æstivation is often found in these buds (Figs. 360, 429, 471, 475, 584). The first and third leaves, in the following chapters, are most frequently alluded to as the “anterior,” the fourth and fifth as the “lateral” leaves. The reversed arrangement, with the median sepal in the front, occurs for instance in Papilionaceæ (Fig. 511), Lobeliaceæ (Fig. 594), Rhodoracecæ. If any bracteoles are present below a tetramerous flower, the relation is generally that 2 sepals (the first ones) stand in the median plane, the two next ones transversely (Fig. 393), and the corolla then adopts a diagonal position (Fig. 397); but a diagonal position of the calyx generally shows that the flower is not, strictly speaking, tetramerous, as in Plantago (Fig. 567), Veronica (Fig. 559 C) and others.

If the bracteoles are not typically present, then the position of the sepals is changed accordingly, and the two outer sepals endeavour to assume the position which the bracteoles would otherwise have occupied, e.g. in Primula (Fig. 547). Other positions are also found when the number of bracteoles is more or less than two.

The leaves which follow the sepals occupy definite positions with regard to them, which we may consider later. An arrangement must, however, be mentioned here; when the flower is “diplostemonous” that is, has two whorls of stamens (thus, Sn, Pn, An + n), these may be arranged in two ways. Either the first-formed whorl of stamens, which are termed the “calyx-stamens,” stands directly in front of the sepals (that is “episepalous”), and is the outermost whorl, and in this case a regular alternation takes place between sepals, petals and the two whorls of stamens, which is also continued into the carpels if their number is the same as that of the other whorls: the carpels are then placed opposite the sepals (Fig. 278) and the flower is isomerous and Gn should be added to the formula above. Or, the calyx-stamens form the innermost whorl, and the corolla-stamens, which are subsequently formed (“epipetalous” stamens), stand outside these (Figs. 360, 429); if the number of carpels is the same as that of the preceding whorls, they are often placed right in front of the petals and the corolla-stamens. The first-mentioned arrangement is termed Diplostemonous, and the second Obdiplostemonous. Both arrangements may be found in one and the same order, e.g. Caryophyllaceæ. The size and relation of the members of the flowers, and also the contact with other members in the early stages of their development, play an important part in determining the arrangement.

The great number of structural arrangements found in this enormously large class, may, as is the case in the Monocotyledons, be further varied by suppression and division of certain leaves (especially the stamens). Instances of this will occur in the following (Figs. 559, 568.—426, 441, 445, etc.).

The Dicotyledons were formerly divided into 3 sub-classes: Apetalæ (those without corolla), Sympetalæ or Gamopetalæ (those with the petals united), and Choripetalæ or Polypetalæ (the petals not united). This division has now been abandoned because it has been proved that the Apetalæ were merely reduced or incomplete forms of the Choripetalæ, and they have therefore been distributed among the various families of the latter sub-class.

With regard to the Sympetalæ (or Gamopetalæ) it may be stated that they form to a very great extent a closely connected and natural group, having in common not only the character that the corolla is gamopetalous and the stamens united with it (this being also found in the Choripetalæ), but also a great many others (such as persistent calyx, cyclic flowers with the formula S5, P5, A5 and as a rule G2, the two carpels being united to form the ovary; seeds with a thick integument and a very small nucellus). They are therefore considered as an independent sub-class, and must be placed at the close of the system of classification as the forms which presumably have arisen the latest. In the future systems of classification this arrangement will very probably be changed, and the first families of the Sympetalæ, the Bicornes and others will for instance be to a certain extent united with the families or orders of the Choripetalæ. The Sympetalæ may certainly be considered as the youngest types, the strongly pronounced metamorphosis supporting this theory, as also the formation of the integument of the ovule, the one thick integument being undoubtedly derived from the coalescence of two—a holochlamydeous ovule, etc.

The Apetalæ and Choripetalæ are united into one sub-class. The leaves of the perianth in this case are, as a rule, free from each other, the structure of the flowers presents many differences, and the ovules have as a rule 2 integuments and a large nucellus. Considerable uncertainty still prevails regarding the arrangement and the relationship of the individual families of the Choripetalæ, and some of the following families are hardly quite natural; but the best arrangement arrived at so far has been adopted here.

At the beginning of the book a review of the orders of the Dicotyledons will be found.

Sub-Class 1. Choripetalæ. Petals free.

Family 1. Salicifloræ.

Trees and shrubs, which, in the structure of the vegetative shoot and the catkin-like inflorescences, resemble the Quercifloræ, but the structure of the flower differs so much from them, that the only order brought under this heading—Salicaceæ—well deserves to be separated and to form a family of its own, the nearest relatives of which are still doubtful. As Juglandaceæ and Myricaceæ also deserve to be placed in a special family, the name Amentaceæ (Catkin-bearers), hitherto applied to all of these plants, cannot be retained as the name of a family.

There is only one order.

Order. Salicaceæ (Willows). Trees with simple, scattered, stipulate leaves. Diœcious. The flowers are arranged in simple inflorescences (spikes or racemes) which are termed catkins, and which fall off as a whole after flowering (♂) or after the ripening of the fruit (♀) (Fig. 322). The perianth is very imperfect[33] or wanting, particularly in Salix (Fig. 323 o); the ♂-flower with 2–several stamens and without any trace of a carpel (a, b, c): the ♀-flower has a free bicarpellate ovary, unilocular, and formed from 2 lateral carpels with 2 parietal (median) placentæ and generally ∞ ovules; the style divides into two stigmas (d, e, f). The fruit is a two-valved capsule and the very small seeds bear a tuft of hairs at the base. Endosperm absent.—The catkins are situated on dwarf-branches, which in some species often develop before the leaves and bear at their base only scale-leaves; in others foliage-leaves are borne beneath the catkins. The vegetative bud commences with 2 bud-scales which are united on the anterior side into a scale. The capsule opens by the dorsal suture. The seed-hairs spring from the funicle.

Salix (Willow) has short-stalked, most frequently lanceolate leaves and erect catkins with undivided bracts (Fig. 322). The flowers are naked; 1 (o in a-f) or 2 yellowish glands situated in the median line. In the ♂-flower generally two stamens, situated laterally like the carpels in the ♀-flower. Various forms are seen in Fig. 323.—The terminal bud of the branches often aborts regularly, the uppermost lateral bud taking its place.

Populus (Aspen, Poplar) has long-stalked, more or less round or cordate leaves with drawn-out apex; catkin pendulous; lobed bracts; perianth cup-like with oblique edge; stamens usually numerous; stigmas often divided.—P. tremula (Aspen) has received its name from the tremor of the leaves: cf. “to shake like an aspen leaf.”

Family 2. Casuarinifloræ.

Trees with verticillate, scale-like leaves forming sheaths at the nodes. Monœcious. Flowers unisexual. ♂-flowers in catkins; ♀ in short spikes. Pollen-tube entering the ovule at the chalaza, and not through the micropyle. Ovary 1-seeded, unilocular. Carpels uniting into a multiple fruit. Only one order.

Order. Casuarinaceæ. Trees (30 species), from Australia and certain parts of S.E. Asia, with peculiar, equisetum-like appearance. The leaves are verticillate, scale-like and united into sheaths. The internodes are furrowed. Branching verticillate. The unisexual flowers are situated in catkins or short spikes. The ♂-flower has a central stamen, surrounded by 2 median, scale-like perianth-leaves and 2 lateral bracteoles. The ♀-flower has a 1-chambered ovary (2 ascending, orthotropous ovules), no perianth, but 2 large, lateral bracteoles which finally become woody and form two valves, between which the nut-like fruit is situated. The multiple-fruits therefore resemble small cones.—Casuarina equisetifolia, cultivated, gives “iron-wood.”

Family 3. Quercifloræ.

Trees and shrubs with small, unisexual, monœcious flowers, having no perianth or a simple inconspicuous one. The ♂ and ♀ flowers are very different and generally placed in separate inflorescences. The ♂-flowers are most often adnate to the bracts. The stamens are placed opposite the perianth-leaves, when they are present in equal numbers. The ♀-flower is naked, or has a superior perianth. The ovary at the base is 2- or 3-(-6) locular with 1 or 2 pendulous ovules in each loculus, only one of which is developed; the fruit is a one-seeded nut; endosperm absent; embryo straight. The inflorescences, which are either compound and mixed (small dichasia in spikes) or simple, are here also termed catkins; but, strictly speaking, this term is applied to the ♂-inflorescences only. In all Quercifloræ the leaves are scattered (usually in 2 rows) simple, and penninerved, and with deciduous stipules.

Order 1. Betulaceæ (Birches). Monœcious, with thick, cylindrical, compound ♂ and ♀ inflorescences (2- or 3-flowered dichasia in a spike with spirally-placed floral-leaves) (Figs. 324, 326, 328). When the perianth in the ♂-flower is completely developed, it is composed of 4 somewhat united leaves, which are placed opposite the 4 stamens (Figs. 325, 326 A). The female flowers are naked; the ovary is bilocular, with two styles and one pendulous ovule in each loculus. The subtending floral-leaves unite with the bracteoles and form a 3–5-lobed cover-scale, which is not attached to the fruit (Figs. 325 D, 326 B). Fruit a nut without cupule (see Corylaceæ and Cupuliferæ). In the bud the leaves are flat. The stipules are deciduous. On germination the cotyledons are raised above the ground. Terminal buds are only found on old Alder trees; the Birch has sympodial branches.

Alnus (Alder) (Figs. 324–326). In the majority of species the ♂-and ♀-catkins are both developed in the year previous to their flowering, and pass the winter naked and bloom before the leaves expand. ♂-flower: 4 stamens. ♀-flower: the 5-lobed cover-scales of the ♀-catkin are woody and remain attached to the axis, so that the entire catkin when ripe resembles a small cone (Fig. 324 b). Each cover-scale supports two winged or wingless nuts. In the native species of Alder the buds are stalked (Fig. 324 k). The bud-scales are formed by the stipules of the lowest leaves.

Betula (Birch). The ♂-catkins, in the native species, appear in autumn, the ♀-catkins in the flowering year on leaf-bearing, short-lived shoots. ♂-flowers: 2 stamens, divided (Fig. 328 A). The 3-lobed cover-scales (Fig. 327 a) of the ♀-catkin are detached from the axis; each cover-scale supports 3 broadly winged nuts (b). The stem has cork with annual rings. The young twigs and leaves have aromatic resin glands.