MOEPHOLOGY OF THE BAKLEY GEAIN. 31 



than are the imported pedigi-eed strains. In one case there is a con- 

 siderable number of siibvarieties from which to choose; in the other, 

 there is a smgle type that has shown superior adaptation to a widely 

 different condition of soil and climate. In any case, whether the 

 means be the acclimatieation of established varieties or the produc- 

 tion of new ones, the problem is not one of the country at large, but 

 is more or less local. It is also a problem in which only the first steps 

 of progress hare been made in this country. 



SUMMARY. 



The integmnents that envelop the ripened seed of barley arise from 

 ioMr sources: The nucellus, the true integuments, the walls of the 

 ovary, and the glumes. Of these, only one has any function other 

 than the protection afforded by dead tissue. The investing mem- 

 brane of the nucellus develops into the semipermeable membrane, 

 which is fomid to have remarkable selective powers. 



In the development of the barley grain the endosperm develops 

 earlier and more rapidly than the embryo, but it is the last to be 

 completed, inasmuch as starch infiltration continues until the parent 

 plant has ceased to live. The first starch is laid down in the center of 

 the flanks of the grain. Infiltration of starch takes place in cen- 

 trifugal order. At matm'ity the starch is less dense about the periph- 

 ery of the endosperm than in the center. The embryo occupies a 

 lateral position with reference to the endosperm at the proximal end 

 of the grain. The epithelial layer is not functional mitil near 

 maturity. 



Germination is the continuation of the growth, of the embryo 

 which was arrested by the maturation of the seed. In its growth the 

 embrs'o utilizes the food stored in the endosperm. 



The conversion of the endosperm is effected by enzyms secreted by 

 the epithelial layer of the scutellum. The cells first affected are those 

 in contact with the epithelial layer. Conversion proceeds from the 

 proximal end slowly toward the distal end, working more rapidly 

 thro'iigh the layers lying inimediately beneath the alcurone layer. 

 CytsLsa and diastase must both proceed from the scuteUuni, and the 

 protcolyl \c ferments most probably owe tlicir origin to the sajne organ. 



Th(; alcurone layer is not a secreting organ. Its function is ])roh- 

 uhly mainly a protective one, although the absorption of its higlily 

 nitrogenous contents by the germinal iiig plantlet occurs at a veiy 

 opportune tinn; in its development. 



The greater diastatic power of small-hcnicd barleys is (hie to the 

 fact that tlie secreting area is prf)portionatcly larger. Th(^ area, of the 

 epithelial layer as a part of the surface of a, sf)heroid nmst (l(>cr(Mise 

 loss rapidly than the volume of the (•n(h)si)('rni ns Ihc si/c of Ihc 

 barley grain is lessened. 



