8 io Stoic ard.—Amyloclastic Secretory Capacities of the 
of objects for plate cultures turns on the fact, fully recognized at the very 
commencement of the inquiry, that the risks of reinfection increase greatly 
with increase in the number of objects handled. This refers more 
especially to objects like aleurone layers and inner endosperms, which have 
to be prepared by careful dissection of the aleurone layer. The successful 
preparation of sterile cultures of endosperms and embryos is a far easier 
task by reason of the more rapid handling of these objects. 
Method of determining copper-reducing power. Many of the earlier 
determinations were made by the standard gravimetric method, the cuprous 
oxide being weighed as such, and the Cu calculated by applying the appro¬ 
priate factor or the oxide reduced in a current of dry H and weighed 
directly. 
The greater number of estimations have, however, been made by the 
extremely convenient and rapid method of Bertrand} 
In every instance these reductions were carried out in duplicate. The 
following comparative results show how closely estimations by the two 
methods approximate each other:— 
l * I 875 grm. of cane sugar were hydrolysed with HC 1 , neutralized with 
Na 2 C 0 3 , cooled and diluted to 250 c.c.; duplicate determinations by the 
two methods made on 10 c.c. of the dilution gave— 
Gravimetric method. Bertrand's method. 
97*2 mg. Cu, 49-5 mg. invert sugar 93-58 mg. Cu, 49 mg. invert sugar 
95.6 ,, Cu, 48.5 ,, „ „ . 92.59 ,, Cu, 48.5 ,, „ ,, 
Theoretically 10 c.c. of dilution contains 49*97 ,, ,, ,, 
Soluble starches employed. The soluble starches used in the digestions 
represent three separate specimens prepared by precisely the same method 
from one and the same stock of potato starch. They were prior to use and 
during the progress of the inquiry subjected to critical control, either with 
a standard malt of known amylolytic power kept for the purpose or by 
means of a standardized enzyme solution. 
The enzyme solutions employed in the following digestions were taken 
from a single embryo-plate culture. 
Comparison of Soluble Starches. 
Starch solids pe r 
Amylase per 20 objects 
100 c.c. of solu¬ 
per hour equivalent to 
Soluble starch. 
tion. 
mg. of Cu. 
A x 
2-62 
90.8 
a 2 
2.67 
85.2 
A3 
2-63 
947 
These values not only show how little these starch preparations differ 
Bertrand: Bull. Soc. Chim., t. xxxv, 1906, p. 1285. 
