PROTEINS 



281 



FIG. 



of a 



251. Section from a cotyleden 

 ghowing a 



Proteins. Proteins are mostly storage forms of food and usually 

 most abundant in seeds, although they are present in all parts of 

 plants. In the kernels of 

 cereals, close to 12 percent 

 of the dry weight is protein. 

 In straw it commonly ranges 

 from 4 to 7 percent and from 

 5 to 8 percent in hay and 

 green fodder. The seeds of 

 the Legumes are especially 

 rich in protein, ranging from 

 about 14 percent in some 

 Lentils to as much as 60 per- ''Q] 

 cent in some Beans. Also 

 the hay of Legumes contains 

 considerable protein. In 



\JL Cd J. Ci. O11VJ VV AlA^j Cl; -LV^ V V/V/O-iO j Vy iAJUJV^X V^rJ.X \A.~ 



vegetables the protein ranges lar space; am> starch grains; aij a i eu rone 

 from about 2 percent in grains; n, nucleur. Enlarged 240 times. 

 Sweet Potatoes to 26 percent After Hayden. 



in Cucumbers. In all fruits there is some protein and sometimes 

 as much as 36 percent in Pumpkins. 



Some of the proteins 

 4> are in solution in the 

 cell sap, but mostly 

 t they are in the form of 

 [-*n . granules or crystals dis- 

 ~&l tributed through the 

 cell among starch grains 

 and other cell con- 

 stituents. (Fig. 251.) 

 Sometimes as in the 

 aieurone layer of cere- 

 als, the cells are filled 

 with protein granules. 

 FIG. 252. Cross section through grain of (Fig. 252.) 

 wheat (Triticum vulgar e)\ p, pericarp; t, testa; p , 

 al, aieurone layer containing numerous protein 



grains; n, nucleus; aw, starch grains. Enlarged ly complex substances. 

 240 times. After Hayden. The f ormu l a g i ve n for 



the protein in the white of an egg is CaggHosOTgNfltfS* They 

 differ from carbohydrates in containing nitrogen, usually 



