Embryo and A leurone Layer of Hor deuni. 807 
ground up with chemically purified sand in a porcelain mortar. When the 
flasks and their contents had acquired the temperature of the thermostat 
(usually after an interval of 10-15 minutes) the finely ground material, placed 
on a small paper chute, was brushed little by little into the digestion flask, 
thoroughly distributed, and by constant agitation mixed with the starch 
solution. 1 
One half of the material serves as th z experimental digestion ; the other, 
added to the alkalinized starch solution, as the corresponding control 
digestion. The latter, invariably carried out in all these digestion experi¬ 
ments, affords the means of correcting for the reducing substances pre-existent 
in the starch solution and added material. 2 
The culture liquid from a given plate was transferred to a calibrated 
tube and its volume brought to 20 c.c. with distilled water. 3 The tube and 
its contents were then transferred to the thermostat, and having attained the 
desired temperature, one half of this volume (experimental digest, 10 c.c.), 
representing the amount of amylase derived from one-half the total number 
of objects under culture, was added and thoroughly mixed with the unalka- 
linized starch solution, the other half (control digest) being added to the 
alkalinized starch solution. The flasks were then securely corked and the 
digestion continued for definite but variable periods of time (varying 
necessarily according to the amylolytic capacities of the material under 
investigation), at the conclusion of which the experimental digests were 
arrested by one or other of the methods already described. Finally, the 
digests were cooled, diluted to 100 c.c., filtered, and the copper-reducing 
power determined on an aliquot portion of the clear filtrate. 
The amyloclastic capacity deduced from the experimental data thus 
determined is expressed throughout in this paper in terms of the weight of 
copper found, in milligrammes, and by calculation referred to the generative 
or secretory capacity possessed or displayed by twenty objects, and further 
reduced to a comparable basis by calculating the output (amylase in the 
culture medium) or augmentation (amylase in the tissue of enzyme) for 
a uniform period of digestion of one hour. 
Throughout it is to be noted that the evaluation of this capacity refers 
1 Unless this method of transferring the material is adhered to (i. e. if the finely ground material 
is added to the starch solution en masse ) ‘ balling’ invariably ensues, and this may be so pronounced 
as to prevent a portion of the enzyme from gaining access to the starch solution during the earlier 
phase of the digestion, and may constitute a source of quite considerable error. 
2 For the purpose of checking this method of arresting amylolytic action, and further to unmask 
any possible action of the alkali on reducing sugars present, in many instances the controls were also 
checked by boiling the mixture of starch solution and material. No objection can be raised to the 
former method provided the use of large excess of alkali is avoided. The foregoing statement applies 
also to the arrests of the experimental digests by the alkali method. 
3 The distilled water employed in these experiments in the preparation of starch and nutrient 
solutions was prepared by means of a copper still modelled specially on the design given by Ford 
(Journ. Inst, of Brewing, ix, 1907 (5), p. 206). 
