573 
Structure of Acer Pseudoplatanus. 
copoeia was taken as a standard and 
on the precipitation phenomena were 
the following table: 
Parts ‘ Pure 
Parts 
Glycerine B. /’. 
A</. Dest. 
100 
— 
75 
25 
5 ° 
50 
2 5 
75 
10 
90 
the effects of varying dilutions of this 
studied, with the results indicated in 
Result. 
No globules formed. 
No globules formed as a general rule: a few 
transient globules occurred in one section. 
Immediate precipitation of globules, followed by 
rapid disappearance within twenty minutes. 
Precipitation of globules almost immediate. 
Solution of globules complete in about two hours. 
Precipitation of globules within a few minutes, 
followed by slow solution. Several hours 
elapse before solution is complete. 
It would seem probable that the proteins are immediately soluble in 
glycerol which contains relatively small amounts of water, and that the 
explanation of the slow disappearance of the globules in the higher dilutions 
lies in the gradual concentration of the glycerol owing to the evaporation of 
the water. Although the usual chemical tests for proteins did not give 
clearly defined results owing to the obscuring effects of the general proto¬ 
plasm, ^ number of digestion experiments were tried with sterile pepsin and 
trypsin extracts. Whilst the majority of the globules were dissolved by the 
pepsin some were resistant: all, however, were digested by the trypsin. This 
difference in behaviour indicates the presence of at least two proteins, and is 
borne out by the fact that whilst, when mounted in io per cent. KOFI, all 
the globules disappear within 24 hours, the rate of disappearance is differen¬ 
tial, some going relatively quickly, others very slowly, and also by the 
staining reactions, some staining much more deeply than others with iodine 
solution, whilst some take aqueous gentian violet well and others remain 
clear and refringent. Like the starch grains, the reserve proteins are 
generally distributed through the parenchyma of the embryo and young 
seedling : they are absent from older seedlings. 
• The third type of reserve substance occurring in the sycamore is of 
a fatty nature} and was chiefly studied in sections which had been treated 
with trypsin solution to remove the proteins, and in some cases with diastase 
solution also to remove the starch. The fatty substance, which, like the 
proteins, occurs as globules, is also generally distributed, but appears to be 
specially abundant in and near the outer cell layers of the cotyledons. After 
preliminary treatment to remove the proteins, the action of various solvents 
was tested in two ways, namely, by immersing thin sections in each of the 
solvents for 24 hours and then staining with a specific stain, and also by 
staining with a specific stain and mounting in each of the various solvents 
1 The authors are indebted to Professor J. H. Priestley, of Leeds, for several helpful suggestions 
in this section. 
