OF TIGRIDIA. 15 
the part which projects, and which is tubular and nearest the 
hilum of the ovule; it is open at its free extremity—the 
micropyle—and is traversed by a canal, leading from this open 
extremity to the body of the nucleus—the canal of the micro- 
pyle. Its structure is cellular, the cells being long ovals, 
their long axes being parallel to the canal. The orifice is 
formed by a circular series of these cells (fig. 4, c; 
fig. 2, c*). The body of the nucleus is joined to the neck, and 
at the point of junction the canal ceases. The rounded end 
of the body is imbedded in the cell structure of the ovule, 
and at this early stage is barely cellular; but nearer the 
neck, square cells (fig. 2, d”), with a cell-nucleus in each, 
are seen. The contents of the body of the nucleus at this 
period are fluid; there are neither granules nor cells in it, 
and the canal of the micropyle is in existence, but barely patent. 
2. At this period the external coat has covered all but the 
free third of the neck of the nucleus; the canal of the micro- 
pyle is recognised by a dark line in the axis of the neck, 
and the micropyle is more open and better rounded (fig. 2, 
a, 6, c.) The same plan of manipulation as in 1, sets free 
the nucleus, whose body is now seen to be perfectly cel- 
lular outside, and filled with more than a simple plasma or 
fluid. Proceed now as follows:—Having obtained several 
nuclei free from their external cell-coats, take a fine-pointed 
knife and operate, under the 13-inch object-glass. Glycerine 
and water, plain water, and olive oil, are good media, and 
should be tried separately. Pierce the nucleus at its round 
extremity, and place it under a piece of thin glass; use the 
handle of the knife as before, and with a little jerking pres- 
sure a delicate globular-looking film will escape through the 
rent in the nucleus. This is the early embryo-sac; it is of 
tolerable distinctness, being composed of a very fine layer of 
cells, forming a membrane and enclosing a quantity of fluid. 
The embryo-sac nearly fills the body of the nucleus, and its 
contents are not granular; neither is there any trace of cell 
growth in them. 'The membrane of the sac is so delicate that 
the edges of its cells are barely distinguishable, but their 
position may be inferred from the presence of cell-nuclei 
(fig. 2, e). It requires an object-glass of +-inch focus 
to determine the structure of the embryo-sac, but one of 
4-inch focus is sufficient for the examination of the nucleus ; 
but in all cases, the lowest power must precede the employ- 
ment of the higher. 
The anterior extremity of the embryo-sac, when it is within 
the nucleus, is in contact with the canal of the micropyle; 
and the effect of the cylindrical shape of the nucleus at this 
