THE BOOT. 



79 



has only one cotyledon or true seed-leaf (Fig. 128, &c.) ; the other 

 leaves, if any are appai-ent, are enclosed by the cotyledon and be- 

 long to the plumule ; and the embryo with one cotyledon is ac- 

 cordingly termed Monocotyledonous. The difference in tliis 

 respect coincides with striking differences in the 

 structure of the stems, leaves, and blossoms, and 

 lays a foundation for the division of Flowering or 

 Phasnogamous plants (114) into two great Classes. 



129. In a few plants, such as Pines, the embryo 

 is provided with from three to ten cotyledons, 

 which expand into a circle of as many green leaves 

 in gei-mination (Fig. 133, 134) : such an embryo 

 is said to be Polycotyledonous, i. e. of many 

 cotyledons. 



130. Having talcen this general survey of the 

 development of PhiEnogamous plants from the 

 seed, and of their common plan of growth, their 

 further development and their morphology may 

 best be studied by examining in succession the three universal 

 organs of vegetation (116) of which they all consist, viz. the Root, 

 Stem, and Leaves. 



CHAPTER III. 



OP THE ROOT, OB DESCENDING AXIS. 



131. The Root is the descending axis (120), or that portion of 

 the body of the plant which grows downwards, ordinarily fixing the 

 vegetable to the soil and absorbing nourishment from it. As already 

 mentioned (121), the root grows in length by continual additions of 

 new fabric to its lower extremity, elongating from that part only or 

 chiefly ; so that the tip of a growing root always consists of the most 

 newly formed and active tissue. It begins, in germination, at the 

 root-end of the radicle. That only this extremity of the radicle is 

 root is evident from the mode in which the radicle grows, namely. 



FIG 133. Section of a seed of a Pine, with its embryo of several cotyledons. 134. Early 

 seedling Fine, with Us stemlet, displaying its six seed-leaves. 



