The natural history of plants, their forms, growth, reproduction, and distribution; . ed, the cotyle-dons throw off the seed-coat unaided, but this is not always the case. In manyinstances their apices remain squeezed up in the cavity of the husk, stunted andyellow, and this reacts injuriously on the seedling, often causing weakness andeven death. It is therefore a mistake for gardeners to plant seeds in loose earthwhere no good hold is afforded, since then, on germination, the seed-coats are raisedup by the only half-liberated cotyledons, whose apices are still imprisoned. 4 COTYLEDONS. 621 W
The natural history of plants, their forms, growth, reproduction, and distribution; . ed, the cotyle-dons throw off the seed-coat unaided, but this is not always the case. In manyinstances their apices remain squeezed up in the cavity of the husk, stunted andyellow, and this reacts injuriously on the seedling, often causing weakness andeven death. It is therefore a mistake for gardeners to plant seeds in loose earthwhere no good hold is afforded, since then, on germination, the seed-coats are raisedup by the only half-liberated cotyledons, whose apices are still imprisoned. 4 COTYLEDONS. 621 With regard to the forms assumed by the cotyledons now withdrawn from theseed under favourable conditions, and which have become green in the sunlight, it isto be noticed that they present far fewer variations than those of ordinary foliage-leaves. Usually their margins are entire, their form elliptical or linear, morerarely circular and obovate. Sometimes the cotyledons are indented in front,resembling a heart in outline; this is especially the case where the embryo is folded ^-f^. Fig. 148.—Cotyledons. 2, 3 Fagus sylvatica. * Fumaria officinalis. * Galeopsis pubescens. « Abies orientalis. i Convolvulus ^Senecio eruemfolius. ^o Mosa canina. ^^ Erodium Cicutarium. ^i Quamoclit coccinea. ^* Tilia Lepidium sativum. 16 Eucalyptus orientalis. is Eucalyptus coriaceus. I-^o Streptocarpus Rexii. in the seed, so that the radicle lies close to the outer margin of the cotyledons, andmay be explained as an economy of the scanty space within the seed. Most rarelyof all the cotyledons are two-lobed (Raphanus sativus), and bisected (Eucalyptusorientalis, Eschscholtzia Californica), three-lobed {Erodium Cicutarium), and tri-sected (Lepidium sativum), four-lobed (Pterocarya Caucasica), and five-lobed(Tilia). It is still to be mentioned that in all seedlings whose hypocotyl is short,the blade of the cotyledons has a long stalk, while in seedlings with elon
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1902
