of locating Sugars in Plant Tissues. 383 
had become quite evident and numbers of large globules were to be seen 
surrounded by smaller ones just in contact with them. 
Besides this gradual grouping and coalescence of yellowish-brown 
globules another change soon became evident. When weak light was used 
a pale yellow substance in the form of more or less regular spheres, often 
with somewhat darker centres, appeared on the lower surfaces of the 
cover-slips. 
This change was first noticed in the stronger mixtures, but later on it 
appeared in the weaker ones also. It was observed on about the third day 
in the 8 per cent, mixture and in those of higher concentration, on the sixth 
day in the 6 per cent, mixture, the twelfth day in the 5 per cent, mixture, 
and some days later in the 4 per cent, mixture. Below this strength the 
pale yellow substance had not appeared after nine weeks from the beginning 
of the observations, although it was then very noticeable in all concentra¬ 
tions above 3 per cent. At the end of this period the first three slides 
showed only globules of brownish syrup of various sizes irregularly grouped 
as described above. (Cf. PI. XVII, Fig. 8.) 
The actual nature of these globules has not been determined, but it is 
considered probable that they were due partly to impurities, either intro¬ 
duced with the osazone or resulting from decomposition produced by local 
overheating, and partly to osazone which had been melted, 1 but had not 
been brought by the heating into a state of fine division, and so had yielded 
visible droplets of syrup. 
At the same time in the 4 per cent, mixture the pale yellow substance 
took the form of numerous approximately regular spheres having a diameter 
of the order of ten times that of the average globule of brownish syrup, of 
which numbers were also present. 
Most of these spheres were single, but in some cases two or more 
appeared fused and occasionally rows of them were formed. 
About five weeks later the 3 per cent, mixture showed a small number 
of these pale yellow spheres. (Cf. PI. XVII, Fig. 9.) After four months from 
the commencement of the observations the number of spheres had increased, 
but none were visible in the 2 per cent, mixture. (Cf. PL XVII, Fig. 8.) 
In the higher concentrations the amount of the light yellow substance 
was proportionately greater. While in the 8 per cent, mixture the spheres 
were for the most part just in contact with one another, above this strength 
their closeness and fusion caused the preparations to appear opaque and 
coarsely granular. 
It has not been possible to make out the exact structure of these 
spheres. In many cases they resembled drops of pale yellow liquid, while 
in a few instances the slightly roughened outline and somewhat granular 
1 Melting-point of maltose phenylosazone, 206° C. Boiling-point of glycerine, 290° C. The 
osazone is liable to decompose in air at melting-point; cf. Armstrong (’ 12 ), p. 60. 
