22 



ANAiYTICAL CLASS-BOOK OF BOTAJST. 



120. Number of Cotyledons. — By far the largest 

 portion of plants have two opposite cotyledons ; a con- 

 siderable number have but one ; while in a single Order, 

 containing the Cone-bearing tribe, or Pines, there are 

 several, arranged in a whorl. This anomalous multipli- 

 cation is, however, now supposed to have been produced 

 by a division of the original or regular number of two. 

 At fig. 12 is such a whorl of cotyledons from the Pine. 

 At t is the common axis ; r is the radicle ; while between 

 the cotyledons, c, may be distinguished the plumule, 

 with its cluster of young leaves. 



121. AcoTYLEDONES. — Plants that have no seed- 

 leaves are called Acotyledones — the particle a, in all 

 cases, when used as a prefix, signifying without. None 

 of the Cryptogamia have any seed-leaves, consequently 

 they are aeotyledonous plants. The Cuscuta, a parasitic 

 plant growing on Milkweeds and other herbs, and com- 

 monly called Dodder, is almost the only instance known 

 of a plant having a regular flower, and yet being destitute 

 of any cotyledon. It is a yellow, leafless vine, with 

 clusters of small, white flowers, and may be seen at fig. 8, 

 with its coiled embryo at the left, which is shown uncoiled 

 just above, where it is seen to be entirely without seed- 

 lobes. 



122. Geemination. — If a seed be placed in favorable 

 conditions, it soon manifests the presence of life by a 

 determination to grow. This first impulse of the life- 

 principle in plants is called Germination. The first 

 motion observed is an extension of the Radicle downward. 

 This soon puts forth from its lower extremity some ten- 

 der little fibres, while at the same time the cotyledons 

 expand, and the plumule, or young stem-bud, appears 

 between them. A plant of the common Garden Bean, 

 fig. 15, represents very happily these initial processes. 

 At fig. 5, the young Bean plant has arrived at another 

 stage. The roots are multiplied, and the stem begins to 

 lengthen upward, bearing the cotyledons, which appear 

 almost too heavy for it to carry ; but they must be car- 

 ried up, because from their substance the young plant is 

 to be nourished until the proper leaves expand, when it 

 will be able to provide for itself At fig. 14 these 

 changes are still more apparent. At fig. 16 the stem is 

 pushing up, and already putting forth the second pair of 

 leaves, while the cotyledons appear yet unexpanded near 

 the roots. At fig. 3 the plant is greatly advanced; the 

 stem is much lengthened, the primordial leaves are fully 

 expanded, while the rudiments of another pair are seen 

 in their axils, or at the terminating point of the stem 



"With none? How many in the Pines ? In the Dodder? In the Orypio- 

 ? First pair of leaves, what called ? First act of life in plants, "what ? 



upward, usually denominated the Axis of Growth. The 

 roots, meanwhile, have enlarged and increased, while 

 among them may be seen the husk of the seed. 



123. The difiorent modes of germination, in Dieo- 

 tyledones and Monocotyledones, are well shown in figs. 

 6 and 7 ; while at fig. 1 1 is a Monocotyledonous seed, 

 the Oat grain, laid open, showing the embryo, g, situated 

 near the base, its radicle, r, and its cotyledon, c, rolled 

 up like a common grass spire. 



124. If the student will be at the pains to make 

 observations for himself, he will find that his studies be- 

 come more profitable and delightful. Let him remove 

 the young seedlings every day or two, for several days, 

 and note every point of progress. He will thus acquire 

 many interesting and valuable particulars which never 

 have been written in books, because, notwithstanding all 

 the uniformity of law, the circumstances of life are so 

 infinitely varied, that they cannot be all rehearsed. 



125. If it were possible to do so, every point and 

 principle should be illustrated and confirmed by an intel- 

 ligent observation of natural forms. Your studies will 

 not then be a mass of hard-sounding and abstruse terms, 

 or of dry uninteresting facts, but they will be vitalized 

 by the presence of Life, and exalted by familiarity with 

 its wonderful revelations. This motto should be the 

 beginning and end of every chapter in Science — Study 

 Nature. 



CHAPTER XI. 



THE DESCENDING AXIS, OE BOOT. 



126. That part of the plant which takes a downward 

 direction, and preferring darkness, hides itself away in 

 the soil, is termed the Root. 



127. Elementary Composition. — The chief bulk of 

 annual and biennial roots is composed of parenchyma (35). 

 The cells, individually considered, are subject to the 

 same laws of life, growth and multiplication, as those of 

 other parts ; but there are some important differences in 

 the general growth of the tissue, as will presently appear. 

 In all plants that form woody stems, the woody tissue 

 appears in the root soon after it begins to be established 

 in the stem. You have observed that trees and shrubs 

 have strong, branching roots, composed chiefly of wood, 

 and corresponding in general with the extent and weight 

 of the stem and branches which they are to fix and 



First motion obseryod ? "What should he studied along with books f 

 General subject 1 Define Eoot Of what composed ? 



