. The classification of flowering plants. Plants. 312 FLOWERING PLANTS [CH. In the capsular fruits the seeds are flattened and generally winged. A small outgrowth, which is sometimes visible in germina- tion opposite the cotyledon (as, for instance, in Tamus), has been regarded as a second cotyledon. According to Solms- Laubach^ the growing-point of the stem is apical, and around it is formed a ring of growth from which proceed both the cotyledon and the second structure, which is therefore probably to be regarded as a development of the sheath- ing base of the solitary coty- ledon. It is to b
. The classification of flowering plants. Plants. 312 FLOWERING PLANTS [CH. In the capsular fruits the seeds are flattened and generally winged. A small outgrowth, which is sometimes visible in germina- tion opposite the cotyledon (as, for instance, in Tamus), has been regarded as a second cotyledon. According to Solms- Laubach^ the growing-point of the stem is apical, and around it is formed a ring of growth from which proceed both the cotyledon and the second structure, which is therefore probably to be regarded as a development of the sheath- ing base of the solitary coty- ledon. It is to be noted that the first leaf of the plumule, and also all later leaves formed on the tuber, have a well-developed sheath. The great majority of the species (more than 150) are included in the genus Dios- corea, which occurs through- out the Avarmer parts of the earth, ascending northwards in America into the United States, and in Asia to China and Japan. A large propor- tion of the species are tropical American. One species which is often separated as a dis- tinct genus under the name Borderea 'pyrenaica, is en- demic in the Pyrenees; a second closely allied species occurs in Chili. They are low- growing herbs, with wingless seeds. Several species of Dios- corea are cultivated throughout the tropics for food on account of the abundant starch in the tuber (Yams); the tuber also con- tains a bitter principle which, however, is removed by washing. Testudinaria contains two species at the Cape. T. Ele- phantipes may be seen in botanic gardens; the tuber, which. Fig, 150. A—G. Tamus communis. A. Flowering branch of male plant, ^ nat. size. B. Male flower, x 3. C. Ra- ceme of fruit, h nat. size. D. Female flower, X 2. E. Upper part of same, the 2 anterior perianth-leaves have been re- moved, the small barren staminodes are shewn at the base of the style. F. Fruit in longitudinal section, slightlj' reduced. G. Seed cut lengthwise shewing small basal embryo, enlarged. B, E, D, after R
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectplants, bookyear1904
