54 



PHARMACEUTICAL BOTANY 



^E A 



Fig. 31. — Section o£ a 

 grain of wheat. A , Pericarps 

 and seed coats; B, layer of 

 cells in endosperm containing 

 aleurone grains; C, cells of the 

 endosperm containing starch 

 grains. (From Hamaker.) 



seminated by wind currents. Examples of these are seen in the Milk- 

 weed, which has a tuft of hairs at one end of the seed called a Coma, 

 and in the official Strophanthus, which has a long bristle-like appendage 

 attached to one end of the seed and called an awn. The wart-like 

 appendage at the hilum or micropyle, as in Castor Oil Seed, is called 



the Caruncle. 



The tegmen or inner coat surrounds the 

 nucellus closely and is generally soft and 

 delicate. 



A third integument, or accessory seed 

 covering, is occasionally present and is 

 called the Aril. Ex.: Euonymus (suc- 

 culent). 



When such an integument arises at the 

 micropyle of the seed , as in the Nutmeg, it 

 is known as an arUlode. 



The Nucellus or Kernel consists of 

 tissue containing albumen, when this sub- 

 stance is present, and the embryo. Albu- 

 men is the name given the nutritive matter stored in the seed. 



MODE OF FORMATION OF DIFFERENT TYPES OF ALBUMEN 



If the egg cell within the embryo sac segments and grows into 

 the embryo and, stretching, fills up the cavity without food mate- 

 rial laid down around it, it happens that the nutritive material lin- 

 gers in the cells of the nucellus pressing around the embryo. This is 

 called Perispermic Albumen. Seen in the Polygonaceas. 



In by far the greater number of Angiosperms, the endosperm nu- 

 cleus, after double fertilization, divides and redivides, giving rise to 

 numerous nuclei imbedded in the protoplasm of the embryo sac out- 

 side of the developing embryo. Gathering protoplasm about them- 

 selves and laying down cell walls they form the endosperm tissue 

 outside of the embryo. Into this tissue food is passed constituting 

 the^Endospermic albumen. 



In the Marantaceae, Piperacese, etc., nutritive material is passed 

 into the nucellar cells causing them to swell up, while to one side a 

 small patch of endosperm tissue accommodates a moderate amount 

 of nourishing substance, thus resulting in the formation of abundant 

 perisperm and a small reduced endosperm. 



