OF THE EMBRYO AND SEEDLING. 



15 



portional to the size and strength of the embiyo, or the degree 

 of its development in the seed. A comparison of the various 

 illustrations sufficiently shows this. Figures 17 to 24 exhibit, 

 in a few common 

 seeds, somewhat of 

 this relation, and 

 also of the position 

 and shape assumed 

 in some instances. 

 The upper rank of 

 figures represents 

 sections of seeds ; 

 the embiyo left in 

 white ; the albumen 

 as a dotted surface. 

 The lower rank shows the embryos detached. That of Mirabilis 

 has very broad and thin cotyledons, a caulicle of equal length, 

 and the whole curved round the albumen which thus occupies 

 the centre of the seed. That of Potato is coiled in the midst 

 of the albumen, is slender ; the cotyledons narrowed down to 

 semi-cylindrical bodies, not leaf-like in appearance, and the two 

 together not thicker than the caulicle. In Barberry the embryo 

 is straight, in the axis of the albumen, which it almost equals ir. 

 length ; the cotyledons considerably broader' than the caulicle, 

 but short and thickish. That of the Peony is similar, but very 

 much smaller, occupying a small space at one end of the albu- 

 men, and seemingly without distinction of parts, but under the 

 microscope and with some manipulation the broader end is 

 found to be divided, that is, to consist of two minute cotyledons. 

 The embryo of a Crowfoot is similar, but still more minute and 

 the parts hardly to be distinguished ; and in some minute em- 

 biyos there is no apparent distinction of parts until they develop 

 in germination. 



28. The study of the formation of the embiyo in the seed 

 teaches that all embryos begin with a still more simple, minute, 

 and homogeneous structure ; and these comparisons suffice to 

 show that all such differences are referable to different degrees 

 and somewhat different modes of the development of the embiyo 

 while yet in the seed. It also appears that the size and shape 



FIG. 17. Section of seerl and contained embryo of Mirabilis (Four-o-clock). 

 18. Embryo detached entire. 



FIG. 19. Section of a Potato-seed. 20. Embryo detached entire. 

 FIG. 21. Section of Barberry-seed. 22. Embryo detached entire. 

 FIG. 23. Section of Peony-seed. 24. Embryo detached entire. 



