534 Piercy . — The Structure and Mode of Life of a 
carbon dioxide, but, on the other hand, arise abundantly in filaments 
cultivated in 2 to 5 per cent, glucose solutions. The results of the 
desiccation experiments indicate that the cells can absorb the granules. 
Additional evidence of this is furnished by the observation that a large 
decrease in the proportion of living cells with granules occurred in a sample 
separated from the material of Experiment I, after two and a half weeks of 
drought, when re-watered (cf. Table I). This was too large to be attributed 
to an increase of living cells by division, such as would account for the 
actual decrease in the proportion of dead cells. 
It might be concluded that desiccation in itself does no immediate 
harm, but that it is the interference with the nutritive processes in the cells 
that causes death primarily. The presence of granules may mean the 
possession of adequate reserves, and hence such cells remain alive for a long 
period. On the other hand, prolonged drought may act directly on the 
protoplasm and bring about death, even in cells which are richly stocked 
with granules. 
In summer, when all activities are at their maximum, such an excess of 
food is produced that enough is available both for growth and the accumula- 
tion of granules (cf. p. 525). In winter, however, there is not enough material 
to support more than growth, and it is only when the latter is inhibited by 
drought that granules make their appearance in any quantity (cf. Experi- 
ment I). 
The production of granules appears to be associated with a definite 
substance in the cell, which is not affected by iodine but stains a deep red 
with Sharlach R. 1 This is almost habitually present, appearing when stained 
as larger or smaller drops distributed in the surface of the protoplasm 
(Fig. 6, A, s.). Under certain conditions it accumulates in the vacuoles at the 
ends of the cell, so that they stain as a whole (Fig. 6 , B, s.), large drops being 
often discernible on a homogeneous ground (Fig. 6 , c). 
Granules have only been observed in abundance in normally growing 
cells when the latter contain a considerable quantity of the substance just 
mentioned. Such was the case with the greenhouse material referred to on 
p. 525, and especially with the filaments cultivated in glucose solutions (cf. 
p. 51 1). The granules produced during a period of desiccation are only 
large and numerous if the material contains a great deal of this substance on 
the advent of drought, and retains it for some time subsequently. This 
happened in the second desiccation experiment ; in fact, as the desiccation 
set in very slowly, the soil remaining damp during the first fortnight, this 
substance showed a preliminary increase, possibly due to the continuance of 
assimilation after growth had ceased. A large proportion of the cells in the 
original material of the first desiccation experiment were primarily well 
1 In some cases the cells became black with osmic acid, and this reaction may be due to the 
same substance. Its general microchemical reactions have not been studied. 
