MORPHOLOGY OF THE BAELEY GEAIN. 17 



a submei-sion for several months in this killmg fluid a living embryo 

 is able to effect the usual processes of conversion. 



That the functions of the scutellum are localized in the epithelial 

 layer is readily shown by experiment. The removal of this layer 

 immediately results in an absolute loss of the scutellum's power of 

 digestion. It is so fuUy incapacitated that no visible corrosion is 

 effected upon a contact surface of starch, when previously such effect 

 was very marked. An epithelial layer, even when not connected with 

 the embryo, seems able to accomplish a slight change, even though 

 no provision for the removal of the products of conversion is made. 



The exact way in which the epithelial layer produces diastase is 

 not known. The change in the plasma, the elongation of the cells, 

 and the peculiar gTanular deposit that accumulates at then' outer 

 ends are all probably connected with the exercise of this function. 

 Indeed, Torrey has gone so far as to assert that this is a deposit of 

 actual enzymatic substance. He asserts that it appears, gathers at 

 the outer end of the cell, and then passes into the endosperm, that 

 the cell stays clear for some time, and that the same phenomena are 

 then repeated. The ^^^.iters have not verified this statement beyond 

 noting that the deposit varied gTeatly in individual grains which were 

 killed at different stages of germination. Sometimes the entire end 

 of the cell was clouded and the outer end heavily charged with a 

 coarse granular deposit, and at other times it was entirely free. 



LOCATION OF DIASTASE SECRETION. 



There are two diastases present in the barley grain: One of trans- 

 location, capable of only weak action; and one of digestion, capable 

 of powerful corrosion. 



The endosperm is incapable of self-digestion other than the slight 

 action of tlie diastaste of translocation. 



The aleurone layer is made up of highly vital cells, which persist 

 until the starch endosperm has been almost completely absorbed. 



The most rapid starch conversion is next to this layer. 



These facts are not sufhcient to ascribe any secretive function to 

 the aleurone layer, the rapid dissolution next to this tissue being due 

 to the fact that from tlieir nature tlie adjacent cells are easier to 

 break down than the ones in the central part of the endosperm. An 

 even more rapid cornjsion follows the furrow, although it is largely 

 composed of ijiactiv<i and dead cells. No coiTosion is to be foimd next 

 t the alcnrojic layer (^Xf<'i)t as tluj chang(^s move outward froju the 

 scutelhiiii. The absence of jncajis to remove tlu^ ])ro(liicts of cojiV(vr- 

 sion at th(^ distal end should not pn^vc^nt the first stages ol' cojvversion 

 taking place; if the aleurone laycT were an active (^ji/yjuatic oi'gaji. 



Tlmt the Hciitclliiiii is active in onzym secretion is shown hy tiu; 

 fact that the fir-.t, chajiges ocr-iir iji l]\<'. layer of (•ji(i()s])ci']ii iti coiiiacl, 



