4 
H. MARSHALL WARD. 
of the outer cells of a zone, at the base of the inner integu- 
ment (cf. figs. 2, 3, 4). The lower of the three cells pro- 
duced by division of the “embryo-sac mother-cell” becomes 
longer, and in its growth compresses, not only the two cap- 
cells, but also the epidermal layer on all sides. It appears 
to absorb the contents of these cells, and the exhausted 
remains easily suffer compression to mere refractive homo- 
geneous masses,' as their greedy neighbour grows. Since 
this cell apparently becomes the embryo-sac we shall here- 
after speak of it as such ; it has now again become about 
as long as at first, and proportionately wider, and its granu- 
lar protoplasm contains a large nucleus. 
During the progress of the changes about to be described 
the two integuments must be pictured as growing up, and 
the inner one closely investing the nucleus and forming a 
micropyle above ; the outer integument never closes in so 
much, but leaves a large loose opening above in later stages. 
Not many cells are formed, but as the embryo-sac becomes 
completed the integument cells elongate very much, large 
sap cavities form, and the nuclei are driven to their walls. 
This is especially the case with the outer integument, and 
at last results in the formation of a large air space between 
the peripheral cells and the base of the nucleus and inner 
integument (cf. figs. 10, 14, 30, &c.) 
About now, or a little later, the pollen-tubes appear in the 
upper part of the ovary as silver' threads, creeping slowly 
down the tissue in the groove formed between the swollen 
placentas and the carpellary walls. They may be few or 
many, and in the latter case can be detected by the naked 
eye on the walls of the ovary if torn open. Owing to the 
prevalence of very cold and wet weather this summer I 
cannot consider the question settled, but believe that the 
further vigorous development of the embryo-sac and contents 
depends on the presence of these tubes. Since insects were 
rare during the bad weather I pollinated many flowers by 
hand, and certainly got more vigorous ovules from the spikes 
so treated, and there were many tubes in these ovaries. In 
cases where the flowers had been pollinated naturally, how- 
ever, the contents of the sac and the cells of the integument 
were brown, and weakly developed. Selecting what appear 
to he normal cases, the following changes occur in the 
embryO'Sac, which by its growth has considerably compressed 
the layer of cells around it, and is capped by the remains of 
the two upper cells (figs. 5, 6, 7, &c.). 
The protoplasm collects into two masses, one at each end 
of the embryo-sac, leaving the centre of the sac filled by 
