196 A TEXT-BOOK OF BOTANY. 



designate a definite protein obtained from wheat, a more distinctive 

 name has been proposed by Osborne, who calls this group " pro- 

 lamins," because all its members which have thus far been hvdrol- 



* 



yzed yield a relatively large quantity of both proline and amide 

 nitrogen. The prolamins are characterized by their solubility in 

 alcohol from 70 to 90 per cent. They are nearly or wholly insoluble 

 in water, but their salts are freely soluble in solutions of acids or 

 alkalies. (See The Vegetable Proteins," by Thomas B. 

 Osborne.) 



GLUTEN is a mixture of proteins occurring in wheat. It con- 

 sists of about 4 per cent, of gliadin (prolamin) and 4 per cent, of 

 glutenin (glutelin). On an average 100 pounds of flour will yield 

 8 pounds of gluten. The " hard " wheats contain more gluten than 

 the "soft' varieties. The gluten of wheat is said to possess a 

 higher dietetic value than the gluten of corn or rye. Crude gluten 

 may be prepared by making a dough with 30 Gm. of flour and 

 about 15 c.c. of water. This is allowed to stand for an hour 

 and the starch washed out by krreading it between the fingers under 

 a gentle stream of tap water. The resultant product is of a 

 grayish color, sticky, tough, and elastic, and when pure is capable 

 of being drawn out into long bands or shreds. The strength of a 

 flour, i.e., its capacity for making a porous and spongy loaf, de- 

 pends mainly on the quality and quantity of gluten it contains. 

 In the preparation of ordinary flour much of the layer containing 

 gluten is separated with the coats of the grain in the course of 

 bolting. Graham flour, on the other hand, being unbolted, has 

 practically the same constituents as the wheat grain itself. The 

 name " gluten flour ' is applied to one in which the greater part 

 of the starch is removed. Gluten flours are used by diabetic 



j 



patients and have a high nutritive value when scientifically pre- 

 pared. 



TOXALBUMINS OR Toxic PROTEINS. Proteins which are ex- 

 ceedingly toxic have been isolated from several plants. That 

 the protein substances possess poisonous properties has sometimes 

 been questioned, but there seems to be no doubt but that true 

 toxalbumins occur not only in seeds, but in other parts of the 

 plant. The following of these principles have been rather care- 

 fully studied: Ricin, found in the seeds of Riciuus communis ; 



