THE SEED. 



137 



edible. In Angiosperms there are usually two seed-coats ; 

 but the Mistletoe (Fig. 65, C) has 

 none at all, and the seed is a simple 

 nucleus from which the embryo pro- 

 trudes. The Filbert and Walnut 

 have but one coat, which is thin and 

 fine. Two-coated seeds are the rule, 

 however, in the Angiosperms. The 

 tegmen is sometimes united to the 

 testa so that it is indistinguishable ; 

 but it is usually free, and often ele- 

 gantly developed. In the Cotton 

 (Fig. 194) the testa is dark (green or 

 black), firm in texture, and append- 

 aged with the long, white, silky hairs 

 which furnish the staple of commerce, 

 is alate, or winged all around (Fig. 195, A). The testa of 

 the Cream-nut is flint-like in hardness, imitating a pericarp, 

 and thus giving the name nut to the seed ; whereas the 

 true nut is the great Monkey-pot, or Cannon-ball, in which 

 these seeds (from 18 to 24 in number) are enclosed. The 

 testa of the Magnolia is fleshy and red, imitating a berry 

 (Fig. 133, B) ; in the Pancratium it imitates a bulb or 

 corm. 



A.CJ 



Fig. 194— Seed of Cotton 

 (GoBsypmiu herbacemn) : testa 

 dark green (seen only at hi- 

 lum, h), covered with a fleece 

 of long white hairs. 



In the Milkweed it 



Fig. 195. — A, sd. of Milkweed {Asclepias incarnata). B, vert. sec. of sd. of 

 Wild Ginger {Asarum canadense). G, vert. sec. of cell and ed. of Castor-oil 

 {Bicinue covmrnmis): c, arillode; /, funiculus; r, luplie ; ch, chalaza; p, peri- 

 sperm surrounding the large embryo, of which the radicle and 1 broad cotyle- 

 don arti seen. D, vert. sec. of ovary of Armeria vulgaris. E, sd. of Common 

 Bean {Faba saliva) : a, hilum ; 6, raicropyle. 



318, The Micropyle is visible in the Pea and Bean, in which it 

 persists as a small hole (Fig. 195, E, &). Often it is closed, and vari- 

 ously enlarged and transformed. In the Milkweed it is Comose, — ■ 

 furnished with a coma, or tuft of long, soft hairs (Fig. 195, A). In 



12* 



