GBOSS ANATOMY OF PLOWBUINQ PLANTS, xll 



B. POLYGTNCEOIAL FRUITS, 



formed by the gyncecia of several flowers. 



1. A spike with fleshy bracts and perianths — 



e.g., Mulberry SoROSis. 



3. A spike with dry bracts and perianths — 



e.g., Birch Strobile. 



3. A concave or hollow, fleshy receptacle, in- 

 closing many dry gyncecia— e.g., Fig . Stconus. 



§7. The Seed. 



The seed is the ripened ovule, and as the ovule consists of a tody, 

 surrounded by one or two coats, or integuments, we may look for 

 a like structure in the seed. However, the 

 modifications which most seeds undergo : 

 render necessary some additional terms. Thus 

 the outer integument is generally so thick- 

 ened and hardened that it is commonly called 

 the testa. The inner is sometimes called the 

 tegmen. In some seeds the outer coat be- 

 comes fleshy, in which case they are iaccate 

 (berry-like) ; in others the outer part of the 



testa is fleshy and the inner hardened, so that Fig. XLIII.— Comose 

 . , J . J /J Ti N /-> seed of Milkweed, 



the seed is drupaceous (drupe-like). Occa- 

 sionally an additional coat forms around the ovule after fertiliza- 

 tion; it differs somewhat in nature in different plants, but 

 all are commonly included under the name aril — e.g. in 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., milk- 

 weed (Pig. XLIII). 



Fio. XLIV.— Embryos dissected outtrom seeds: 1, showing at a the "radicle;" 

 6 6, the fli-st leaves (cotyledons); c, the third and fourth leaves (plumule^. 

 2, a straight embryo. 3, embryo folded upon itself (incumbent). 



