MOEPHOLOGY OF THE BAELEY GEAIlSr. 19 



difference can not be mthout a purpose, and fortunately this pur- 

 pose is easily explained without the necessity of having recourse to 

 any theory of secretion. The aleurone layer undoubtedly exercises 

 a strong protective function. In rainy weather, fungi are invariably 

 to be found mvesting the barley grain and feeding upon the feebly 

 active cells of its envelopes. Their hyphse often run through all the 

 iavestiug layers of the seed without being able to penetrate the 

 aleurone layer. Whether or not it be the vital resistance of its pro- 

 toplasm, the mere mechanical obstacle of its heavily cuticularized 

 walls, or both, this tissue is an effective barrier to the mroads of 

 molds and bacteria. The fact that such protection is of absolute 

 necessity is readily appreciated. Within the endosperm is stored the 

 food upon which the future development of the embryo is absolutely 

 dependent. Even the perpetuation of the species rests upon the 

 proper conservation of this reserve food material. This mass of 

 readily assmiilated compomids is an ideal food for all sorts of sapro- 

 phytic and parasitic organisms. It is therefore not surprismg to find 

 built aromid this material a specialized tissue with a highly protective 

 function. 



The aleurone layer serves a second purpose, but one which alone 

 would hardly justify its existence, in that it appears to be more 

 opportmie than essential. When the plant is first establishing itself 

 in the sod, it utilizes the starch endosperm, a material rich in carbo- 

 hydrates, which seems to meet all the requirements of early growth. 

 \Mien once its green leaves are exposed, however, photosynthesis is 

 able to supply all its needs for starch. With nitrogenous food mate- 

 rial the problem is more difficult. A considerable extension of feed- 

 ing surface in the roots is necessary before such material can be pro- 

 cured in any quantity. The starch endosperm contains an extremely 

 limited amount of nitrogenous matter and that stored in the embry- 

 onic tissues is soon exhausted. The breaking down of the aleurone 

 layer and the utilization of its highly nitrogenous cell contents comes 

 at the critical period in the life of the plantlet when this material is 

 of especial value. This may account for the extra thickness of this 

 layer in certain genera of grasses, of which Hordeum is one of the 

 most notable examples. 



GREATER DIASTATIC POWER OF SMALL-BERRIED AND OF HIGH- 



NITROCiEN BARLEYS. 



It i-, interesting to not(^ that the th(M)7-y of scutellar secretion con- 

 forn)s nifcly lo nn ii|)|)!irently satisfying explanation of a widely rec- 

 ognized fact in till' utilization of barley malt. l)istill(M-s Juivc! long 

 kn<Avn that tlnir n(|iiin'ni('nts un^ best met by a, malt of iiigh dia- 

 static power and iliiit >iii:ill-l)crric(| hjirlcvs of high nitrogen contcjit 

 are best adapted i<» |»ro(lijc.(", surli niiilt. VVitli those brewers wlio 

 arc producing a Ixcr \i\ the niannfiict uic of w hi( li mult luljinicts, such 



