the Grain of Wheat (Triticum vulgar e). 131 
three-day intervals, from about the tenth day after pollination till the time 
of harvesting. 
From these determinations it was possible to make an approximately 
accurate calculation of the quantity of carbohydrate per 1,000 grains— the 
results of which have been expressed as a curve for each of the three plots. 
It is readily seen that, at least in two cases, the curve is very smooth and 
very straight for a period corresponding to about six weeks from the time 
of pollination, while it flattens off considerably during the last week. This 
indicates that the infilling of starch goes on very steadily and regularly for 
about six weeks, the rate of inflow hardly fluctuating at all. Then, shortly 
before the grain is what the farmer would call { ripe ’, this influx practically 
ceases. 
A parallel series of analyses showed that during the whole period 
of starch deposition, protein matters are entering the endosperm at the 
same time, but the stains used to place the starch in evidence for micro- 
scopic work tended to mask the increasing amounts of nitrogenous reserve 
material. 
3. Disorganization of Nuclei. The various changes in the endosperm 
nuclei in the later stages of development were studied on the 1904 material 
chiefly by means of series of hand-sections stained with Delafield’s 
haematoxylin. 
As we have seen, starch has filled into practically all the endosperm 
cells a fortnight before the grain can be regarded as ripe enough to cut, but 
the curves illustrating the inflow of carbohydrates show that starch continues 
to be crammed into the cells for some while longer. Just about the time 
that all the endosperm cells have received some quota of their starch, 
when the grain is just beginning to turn from green to brown, changes 
occur in the nuclei of the cells. Up to this period these have remained 
perfect and complete, rather large in proportion to the size of the cells, 
possessing good nucleoli and taking stains well. Those nuclei in the 
neighbourhood of the embryo are the first to exhibit change, in fact 
disorganization seems to proceed gradually from the tip downwards, in 
exactly the opposite direction to that in which the starch is deposited. 
First of all the nuclei in the middle of the flanks seem to lose their nucleoli 
and become very dense in structure, staining more deeply than those near 
the aleurone layer, which still retain their nucleoli. This change continues 
downwards and outwards as time goes on, though some of the nuclei in the 
sub-aleuronic cells round the furrow retain their nucleoli till quite a late 
stage in maturation. While this is going on a further alteration occurs — 
those nuclei which first become dense apparently lose their solidity, and 
exhibit a network structure in section, at first appearing as very coarse 
networks, with thick walls and relatively small cavities, later as fine reticula 
with large cavities. Investigation showed that this is due to the pressure 
