226 



BOTANY AND PHARMACOGNOSY. 



the gluten layer around the endosperm contains proteins. The 

 number of layers of gluten- or aleurone-containing cells varies in 

 the different cereals. In corn, wheat and rye it consists of but 

 a single layer ; in oat and rice, of i or 2 layers ; while in barley 

 it is made up of 2 to 4 layers. 



The Grasses comprise about 3500 species and are distributed 

 in all parts of the world. While most of the plants are grass-like 

 still some of them, as the bamboos of the Tropics, become quite 

 tall, having woody silicious stems and bearing many branches in 

 the axils of the leaves. They yield the cereal grains forming so 



Fig. 123. 



B 



tlG. 124. 



Fig. 123. Diagrams of cross-sections of monocotyledonous flowers: t, stem of plant; 

 f, bract; s, sepals or outer circle of perianth; p, petals or inner circle of perianth; a, stamens; 

 c, ovary. A, regular flower of the lily; B, irregular flower of iris. Fig. 124. C, flower of 

 an orchid, in which 1 is the lip and SS the two staminodes. .ifter Warming. 



large a proportion of the food of man, and forage constituting the 

 food of many of the lower animals. The following are some of 

 the important cereals: Wheat {Triticiini safiz'um and its varie- 

 ties), corn (Zca Mays), oat {Avena sativa), rice {Oryza saliva), 

 barley (Hordcinn sativum and its varieties), rye {Sccalc ccrcalc). 

 A number of the species yield a sweet cell-sap from which cane 

 sugar is made, of which the most important are the sugar cane 

 (Saccharum ofFicinarum) and sorghum {Audropos^on anindina- 

 ccns saccharatns and other varieties). 



A large number of the grasses are used in medicine, one of 

 which, couch-grass (Agropyron repens), is official (p. 490). 



Agropyron repens is a common perennial grass, forming slen- 

 der jointed rhizomes, by means of which the plant is extensively 





