CHAPTER XIII. THE FRUIT AND SEED. 



II 7 



hilum, which corresponds to the part called the hilum in the 

 ovule. But notwithstanding the structural resemblance in many 

 particulars, the ovule undergoes important changes, not only in 

 size but also in form and structure, in the course of its develop- 

 ment into the seed. Among the most important of these are the 

 following : 



(1) TJie seed-coats, particularly the outer, frequently undergo 

 considerable modification. While the exterior one of the ovule 

 is thin, membranous and smooth, that of the seed, termed the 

 testa or episperm, is usually considerably thickened, and acquires 

 various markings or appendages. 



Fig. 343. 





Fig. 345. 



Fig. 346. 



Fig. 343. — Comose seed of the Milk-weed. 



Fig. 344. — Alate or winged seed of the Catalpa. 



Fig. 345. — Alate seed of the Pine. 



Fig. 346. — Fruit of Nutmeg, with one side removed, to show the seed enveloped in the 



If the testa becomes very thick, hard and resistant, it is 

 termed crustaceous ; if smooth and shining, it is described as 

 polished ; if roughened, it may be tuberculate, pitted, rugose, 

 reticulate, alveolate, fissured, furrowed, hairy, etc.; and if 

 appendaged, the appendages may be in the form of a coma, or 

 long hairs, which either cover the entire seed, as in the Cotton, 

 or only one end of it, as in the Milkweed, Fig. 343 ; or the 

 appendage may be in the form of short silky hairs, as in the 

 seeds of Nux vomica ; or of one or more flattened expansions, 

 called icings, as in the seed of the Catalpa, Fig. 344, and of the 

 Pine, Fig. 345 ; or it may be an outgrowth from the funiculus or 

 placenta, which more or less completely envelops the seed, and 



