The only ones among all the trees that bear nothing whatever, not so much as any seed even, are the tamarisk,2499 which is used only for making brooms, the poplar,2500 the alder, the Atinian elm,2501 and the alaternus,2502 which has a leaf between that of the holm-oak and the olive. Those trees are regarded as sinister,2503 and are considered inauspicious, which are never propagated from seed, and bear no fruit. Cremutius informs us, that this tree, being the one upon which Phyllis2504 hanged herself, is never green. Those trees which produce a gum open of themselves after germination: the gum never thickens until after the fruit has been removed.