10 BULLETIN 183^ U. S. DEPARTMENT OF AGEICULTUEE. 



starch is the result of the action of maltose-forming diastase. The 

 disappearance of the plasmic network of the cells is due to its being 

 peptonized by proteolytic enzyms and thus made soluble for absorp- 

 tion. Chemistry has made known the processes by which these 

 changes are effected. It has found methods to increase the power 

 of the grain to digest these various substances. It has invented 

 ways of manipulation so as to secure the greatest efficiency of the 

 enzyms present. It has not, however, shown any way of increasing 

 the capacity of a grain to secrete enzyms, nor has it discovered any 

 modification of structure that would lead to a greater economy in 

 conversion. 



It is only by a defuiite location of the sources of these energies 

 that a workmg basis for improvement of the barley grain can be 

 obtained. Not only must it be known which of the tissues are 

 concerned in these activities, but the extent and nature of the action 

 of each tissue must be understood. Upon this point there has been 

 much divergence of opinion. The disagreement has been not only 

 as to the parts of the grain concerned, but also as to whether or not 

 the various enzyms are secreted by the same or by separate organs. 

 Since there are three areas in dispute and three enzyms to be ac- 

 counted for, the number of possible hypotheses has occasioned a 

 very considerable confusion. 



RESUME OF THE CONCLUSIONS OF OTHER INVESTIGATORS. 



Although the number of investigators who have been interested 

 in one or several phases of this subject is great, a brief statement of 

 their conclusions is necessary at this point. 



Krabbe ^ assigns all diastase secretion to the individual cells of the 

 endosperm, based on his assertion that diastase can not pass from 

 cell to cell. 



Green - finds in Ricinus communis a marked ability of the endo- 

 sperm for self-digestion. 



Hansteen ^ finds that the endosperms of Zea Tnays and Hordeum 

 vulgare are capable of self-digestion when products of conversion are 

 removed, that the aleurone does not supply the diastase, and that 

 the scuteUum is capable of vigorous corrosion of adjacent starch. 



Pond,* in an exhaustive chemical research, fails to discover any 

 ability for self-digestion in the date. 



1 Krabbe, G. Untersuchungen iiber das Diastaseferment unter specieller Beriicksichtigimg seiner 

 Wirkung auf Starkekomer irmerhalb Pflanze. Jahrbiicher fiir Wissenschaftliche Botanik [Pringsheim], 

 Bd. 21, Heft 4, p. 521-561, pi. 13-15, 1800. 



- Green, J. R. On the germination of the seed of the castor-oil plant (Ricinus communis). (Abstract.) 

 Proceedings, Royal Society, London, v. 47, no. 287, p. 146-147, 1800. 



3 Hansteen, Barthold. Ueber die Ursachen der Entleerung der Reservestofie aus Samen. Flora, Bd. 

 79, p. 419-420, 1894. 



* Pond, R. 11. The incapacity of the date endosperm for self-digestion. Annals of Botany, v. 20, no. 

 77, p. 61-77, 1906. 



