OF THE ORGANS OF VEGETATION. 27 



actually wanting, a correlation with its parasitic mode of life. 

 (64, Fig. 78.) 



43. The dicotyledonous and the monocotyledonous character 

 of the embryo is correlated with profound differences in the whole 

 ulterior development, as revealed in the structure of the stem, 

 leaves, and flower ; which differences mark the two great divisions 

 of Phaenogamous plants, viz. DICOTYLEDONES or DICOTYLEDONOUS 

 PLANTS, and MONOCOTYLEDONES or MONOCOTYLEDONOUS PLANTS, 

 names introduced into classification by Ray, and adopted by 

 A. L. Jussieu, in his Genera Plantarum. 



CHAPTER III. 



MORPHOLOGY AND STRUCTURE OF THE ORGANS OF THE 

 PLANT IN VEGETATION. 



SECTION I. OF THE ROOT. 



44. The Root, which has been called the descending axis, is 

 that portion of the body of the plant which grows downward, 

 ordinarily fixing the vegetable to the soil, and absorbing from it 

 materials which the plant may elaborate into nourishment. As 

 alread}* stated (24), the root grows in length by continuous 

 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 normally 

 begins, in germination, at the root-end of the 

 caulicle, or so called radicle. But roots soon 

 proceed, or may proceed, from other parts of 

 the stem, when this is favorably situated for 

 their production. The root does not grow 

 from its naked apex, but from a stratum 

 immediately behind it : consequently its blunt 

 or obtusely conical advancing tip consists of older, firmer, and 

 in part effete tissue. The tip of all secondary roots and rootlets 



FIG. 61. Magnified tip of root of a seedling Maple (such as in Fig. 9), sufficiently 

 enlarged to indicate the cellular structure: a. the portion where growth is taking 

 place; 6. the older ami firmer tip. 



