122 Brenchley. — On the Strength and Development of 
this was easily known by its position and also by the fact that it was usually 
a trifle larger and better developed than those above and below. To ensure 
that a second grain was never selected from the same ear the ends of the 
marking wool were clipped off close to the knot. The material thus 
collected was fixed in the field, half in Flemmings weak solution and half 
in acetic alcohol. It was found that immersion in Flemming’s solution for 
any length of time had a decided tendency to blacken the grain ; indeed, 
in the younger stages, this discoloration penetrated right through the 
tissues. Attempts were made to shorten the time of immersion, even 
reducing it to half an hour, but while the blackening still occurred to some 
extent, fixation was imperfect. Much better results were obtained by 
killing and fixing in acetic alcohol for twenty minutes, washing out well 
in two or three changes of spirit, and preserving in a mixture of one-third 
glycerine, two- thirds spirit. As with the 1904 material, the grains were 
embedded through bergamot oil and cut in microtome series. Various 
stains were used, including Flemming’s triple stain, brasilin, Ehrlich’s 
haematoxylin (also with O. G. or eosin), but the best results were obtained 
with Heidenhain’s and Delafield’s haematoxylin (either with or without 
O. G.). 
Material was collected from all the three plots mentioned, but as the 
sequence of events was parallel in all, attention will be chiefly confined to 
that obtained from Plot 3, Broadbalk, (Square Head’s Master). 
(b) Early Stages of Development. 
The ovule of wheat is anatropous, curved on its funicle, so that the 
micropyle is brought to face inwards towards the stalk of the ear. For 
the sake of convenience the micropylar end will be consistently referred to 
as the tip of the grain. 
Assuming that pollination in the wheat occurs on the same day that 
the flower opens, the earliest stage in the material at hand is that taken 
two days after pollination, though one grain of this date seems a trifle less 
advanced than the rest. In this case the ovule is cut rather obliquely 
through the micropyle, and shows a mass of nucellar tissue still present, 
bounded on the periphery by a single layer of very regularly arranged 
square-shaped cells, with well-developed nuclei, which eventually merges 
itself in the tissues of the placenta to which the ovule is attached. Outside 
this layer are one or two more rows of cells which seem to have broken 
away from the surrounding pericarp in the process of fixing and preparing. 
Within the nucellus the boundary line of the embryo-sac can usually be 
made out, though in places it is disintegrating or destroyed. At the tip of 
the grain, just where the position of the micropyle is indicated, is a group 
of two or three nuclei. One of these is a synergid, distinguished by its 
dense appearance, and there is some indication of the second synergid. 
