OEGA^rS OF EEPRODrCTIOX. 



3il 



radicle is different, the latter may form an acute, obtuse, or 

 right angle to them ; or be folded back to such an extent as to 

 lie parallel to the cotyledons : in the latter case, the radicle may 

 be either applied to their margins, as in the Wallflower {fig. 759), 

 when the cotyledons are said to be accumbent ; or against the 

 back of one of them, as in Isatis {fig. 7oS), when the cotyledons 

 are incurabent. These terms are chiefly used in reference to 

 Cruciferous Plants (see Cruciferse), which are best arranged ac- 

 cording to the manner in which the different parts of the embryo 

 are folded, and their relative positions to each other. 



Having now described the general characters of the monoco- 

 tyledonous and dicotyledonous embryo, we have, in the last place, 

 to allude briefly to the relation which the embryo itself bears to 

 the other parts of the seed, and to the pericarp or loculus in 

 which it is placed. 



Belation of the Embryo to the other Paints of the Seed, and to the 

 Fndt. — In the first place with regard to the albumen. It must 

 necessarily happen that when the albumen is present, the size 

 of the embryo will be in the inverse proportion to it; thus in 

 Grasses {fig. 689) we have a large deposit of albumen and but a 

 small embryo, while in the Nettle {fig. 760), the embrj-o is large 

 and the albumen small. The embryo may be either external to 

 the albumen {figs, 689 and 763) and thus in contact with the in- 



Fig. 760. 



Fig. 761. 



Fig. 762. 



Fig. 763. 



Fig. 760. Tertical section of tlie achtenium of the Nettle, containing a 

 single seed. t. Intecuments of tlie seed. pi. Placenta, r. Radicle. 



St. Stigma. Fig. 761. Vertical section of the fruit of the Dork (liu- 



mex). ov. Pericarp, inic. Micropyle. ph Embryo towards one side of 

 the albumen, alb. ch. Chalaza. Fig. 762. Vertical section of the car- 

 pel of Mirabilis Jalapa, containing one seed. a. Pei-icarp. s. Style. 

 e. Peripherical embryo with its radicle, r, and cotyledons, c. p. Albu- 

 men, t. Integuments of the seed. Fig. 763. Vertical section of the 



seed of Lychnis dinicu. te. Integuments, emb. Embryo on the outside 

 of the albumen, alb. 



