TISSUES OF AN0I0SPEBM8. 437 



laceae there are numerous achenes on a prolonged receptacle ; in Mag- 

 nolia numerous I'ollicles are similarly arranged ; in the raspberry many 

 drupelets cohere slightly into a loose mass, which separates at maturity 

 from the dry receptacle ; in the blackberry similar drupelets remain 

 closely attached to the fleshy receptacle ; in the strawberry there are 

 many small achenes on the surface of the fleshy receptacle ; finally, in 

 the rose several to many achenes are enclosed within the hollow and 

 somewhat fleshy receptacle. 



B. Polygyncecial fruits, formed by the gynoecia of several flowers. 



1. A spike with fleshy bracts and perianths — e.g., 



Mulbtrry Sokosis. 



2. A spike with dry bracts and perianths — e.g.. 



Birch Steobilb. 



3. A concave or hollow, fleshy receptacle, enclosing 



many dry gynoecia— e.g'., Pig Sycokus. 



The Seed. — Many of the terms used in the description of the ovule 

 are applied also to the seed. However, the modifications which most 

 of the parts undergo render necessary some additional terms. Thus 

 the outer integument is generally so thickened and hardened that it is 

 commonly called the testa. The inner is sometimes called the tegnien. 

 In some seeds the outer coat becomes fleshy, in which case they are 

 baccate (berry-like) ; in others the outer part of the testa is fleshy and 

 the inner hardened, so that the seed is drupe-like (drupaceous). Occa- 

 sionally an additional coat forms around the ovule after fertilization; 

 it differs somewhat in nature in different plants, but all are commonly 

 included under the name aril — e.g.. May Apple. 



The testa may be prolonged into one or more flat extensions ; such a 

 seed is winged — e.g., Catalpa. Its epidermal cells may be prolonged 

 into trichomes, forming the comose seed — e.g., cotton. 



The embryo either occupies the whole of the seed cavity, in exalbu- 

 minous seeds, or it lies in or in contact with the endosperm, in the 

 albuminous seeds. It is straight — e.g., the pumpkin; or variously 

 curved and folded — e.g., in Erysimum,, where the cotyledons are in- 

 cumbent, and in Arabis, where they are accumbent. 



537.— The Tissues of Angiosperms. — The epidermis of 

 Angiosperms does not difier in any marked way from that 

 of the Gymnosperms and the Pteridophytes. The principal 

 differences are that, as a rule, the stomata are more numer- 

 ous, and the trichomes, which are much more commonly 

 present, show greater variations in form and structure. It 

 is noticeable, furthermore, that in both these points the 

 Dicotyledons ezcel the Monocotyledons. 



