88 



ANALYTICAL CLASS-BOOK OF BOTANT. 



extended in its whole length, and forms the stem. The 

 young plant is nourished hy albumen, starch, and other 

 nutritious substances contained in the seed, until it has 

 developed a root and leaves, when it becomes entirely 

 self-dependent, procures its own food, and elaborates the 

 substance of its own tissues. But as starch is insoluble 

 in cold water (57), and the vegetable tissues cannot take 

 up solid particles, this highly nutritive substance, being 

 acted on by certain azotized substances contained in the 

 seed (71), is decomposed, and converted first into dex- 

 trine, which, you will remember, is soluble in cold water, 

 and then into sugar. In most dicotyledonous plants, 

 the cotyledons rise out of the ground, and, expanding 

 into a pair of thickened leaves, as in the Garden Bean, 

 fig. 16, contribute to the nourishment of the young plant, 

 not only by their fleshy substance, but by developing 

 chlorophylle (65). The germination of a monocotyledonous 

 plant is well shown in the Oat, fig. 19, and the Maize, fig. 

 1 7 ; and that of a Dicotyledonous plant at fig. 1 6. 



507. The periods that elapse between the times of 

 planting and germination in seeds, range from a few days 

 to two years. Cabbage will germinate, in two days, 

 the Turnip in three. Grasses in a week, Hyssop in a 

 month, some Pines in a year, and the Holly in two 

 years. 



508. Since the facts of this chapter embrace many 

 principles which are dry and difficult in their very na- 

 ture, they may be made more familiar by reviewing them 

 collectively. The Seed consists of a Nucleus and its 

 Integuments. The external Integument is the Episperm, 

 the interior one the Endosperm, the latte)i not always 

 being present. The parts of the Nucleus are the Albu- 

 men and Embryo, the albumen not always present. The 

 opening in the integuments of the ovule is the Foramen ; 

 the part to which it is attached is the placenta ; the stalk 

 which unites it to the placenta is the Funiculus ; the 

 base of the ovary which is joined to the funiculus, and in 

 separating leaves a scar, is the Hilum ; and the point 

 from which are sent off nutritive vessels between the 

 nucleus and its integuments is the Chalaza. The nu- 

 cleus receives the influence of the pollen through the 

 foramen, and its nourishment from the placenta, through 

 the funiculus. In fig. 10, which represents a vertical 

 section of the Garden Pea, g is the embryo, t its common 

 axis, r the radicle, m is the foramen, te the episperm, e 

 the endosperm, c the fleshy cotyledon, ch the chalaza, 



Is the Primary A.xi? Eoirt or Stem (115) ? By wliat is tiro young plant 

 nourished — how long? Why will not the vegetable tissues take up starch? 

 Under what form will they do so ? In what plants do the Cotyledons rise out 

 of ground— "What form— liow useful ? How soon will the Cabbage plant ger- 

 minate—Turnip — Gratses- Fines — Holly? Recapitulate. Y/hat circum- 



rap the nutritive vessels, and pi the placenta. The 

 cells containing albumen and starch are seen in the seed 

 of Rye, fig. 15. At fig. 9 is seen the whole fruit of the 

 Pea. Its parts have lately been explained. Recall 

 them. 



DISSEMINATION OF SEEDS. 



509. Blany circumstances assist in this great work. 

 The plumose appendages of the Compositse, of which the 

 Thistle-down is a familiar instance, waft the seeds through 

 the air, often to a great distance. A seed of the Robin's 

 Plantain, one of this Order, was carried across the At- 

 lantic in a stufied bird, about the middle of the seven- 

 teenth century, and now it has overspread all Europe. 

 A similar instance of exotic dissemination is furnished 

 by the Cardoon Thistle, which is native of Southern 

 Europe and Northern Africa. The seeds of this plant 

 having been conveyed by some means to La Plata, its 

 progeny have overspread the great Pampas of the Cordil- 

 leras, for nearly two hundred miles in eveiy direction. 

 They cover whole tracts so closely with their stout stems 

 and spinescent leaves, that no animal can get through the 

 impenetrable barrier, which is sufiioient to repel an in- 

 vading army. The seeds of many others of the Compos- 

 itse are furnished with hooks and spines, which adhere to 

 the fur of animals, and to other bodies ; while those of 

 the Ash, Beech, and Maple, spread their wings, and fly 

 abroad on the same great errand. River and ocean cur- 

 rents also assist in the dispersion of seeds. Those of the 

 Cocoa-nut and Mahogany are transported from tropical 

 America to the North Cape, and many others make 

 similar voyages. Some flowers, as the Balsamine, fig. 9, 

 have elastic pericarps, which in bursting scatter the seeds 

 at a considerable distance. Seeds are also carried in the 

 stomachs of birds, or they are stored up by animals for 

 their winter food, and thus planted at a distance from 

 the parent soil ; and in this way forest trees are often 

 propagated. Even little children, as with their light 

 breath they blow away the downy seeds of the Thistle 

 and Dandelion, or slyly fasten the hooked Burdock fruits 

 in each other's clothes and hair, are unconsciously assist- 

 ing in this great work of the Creator. 



LONGEVITY OF SEEDS. 



510. Some seeds lose their vitality almost as soon as 

 they fall from the plant, but many are very tenacious of 

 life. The seeds of Grasses often preserve their vitality 

 for a long period. Maize and Rye will germinate after 



stances assist in dissemination of seeds? How in tlio Compositai— tlie Balsam- 

 ine— AVingttd seeds? What effect liave river and ocean currents— birds— 

 quadrupeds- sports of children ? Fact of Robin's Plaintain — of the Cardoon 

 Tliiitle? Comparative longcxity of seeds? How in Grasses, Maize, and I'.vi.. 



