§37 
Embryo and Aleurone Layer of Hordeum . 
no appreciable reduction in the mass of inner endosperms takes place even 
when the culture period covers 14 to 20 days, the actual weights of the 
objects in Experiments 3 to 6 after 24 hours’ desiccation at 30° C. were 
determined, and also for comparison the initial average weight of 5 inner 
endosperms similarly prepared and steeped only. 
The influence of the phosphate in concentrations ranging from P 2 to P 4 
appears to be in some way detrimental to the amylase which passes by 
diffusion into the medium. 
Inner endosperms (Table XVII, p. 833) on agar alone apparently, as 
judged by the amount of reducing sugar in the medium, exhibit greater 
depletive power than on the same medium with the addition of mineral 
salts. 
The evidence so far accumulated again tends to show that, while the 
inner endosperm does exhibit an auto-depletive capacity, that capacity is, 
as compared with that possessed by the endosperm, relatively limited. 
IV b. Cultures of Endosperms and Inner Endosperms on Moist 
Calcium Sulphate. 
Under the experimental conditions described in the preceding sections 
the quantitative method employed elicited two important facts, viz. that the 
isolated inner endosperm possessed a capacity for augmenting its amylase 
content, and an auto-depletive capacity, both of which, however, are inferior 
to the similar capacities possessed by the endosperm. Since the endosperm 
for our purpose consists of inner endosperm and aleurone layer, and since 
evidence has been adduced showing that the latter tissue is to be regarded 
as a secretory tissue, the marked signs of depletion which the endosperm 
exhibits may fairly be attributed to the action of an active amylolytic 
enzyme elaborated by the cells of the aleurone layer. 
General considerations derived from a survey of the foregoing experi¬ 
mental results indicated that, as in all biological problems, the relation of 
the object 1 to its substrate is an important consideration. 
The employment of gelatine or agar media involves the use of sub¬ 
strata whose chemical reaction may vary from time to time within quite 
small limits, yet slight changes in this respect may introduce factors whose 
influence it is at once difficult to detect and control. It was therefore 
necessary to choose a single and preferably neutral inorganic substance in 
order to ensure the uniformity of the substrate. 
1 As will be pointed out later, we are probably dealing, in the case of inner endosperms, with the 
relation of an enzyme to its substrate. 
