238 CONTRIBUTIONS TO 
will, probably, on more accurate investigation, be mostly re- 
duced to one of these substances. These substances, however, 
soon become dissolved, and converted either into sugar or gum; 
both changes take place at times, even before the pollen-grain 
has commenced to send forth tubes upon the stigma, frequently 
during the gradual descent of the pollen-tube through the 
style to the ovule; so that in some cases unaltered starch may 
still be found even in the embryonal extremity. 
At both these situations the before-mentioned minute 
mucus-granules are very soon developed in the gum, upon 
which the solution of gum, hitherto homogeneous, becomes 
clouded, or when a larger quantity of granules is present, 
more opaque. Single, larger, more sharply defined granules 
next become apparent in the mass (fig. 2, the upper part) ; 
and very soon afterwards the cytoblasts appear (fig. 2, the 
lower part), looking like granulous coagulations around the 
granules. The cytoblasts, however, grow considerably in this 
free state; and I have observed, in Fritillaria pyrenaica for 
instance, a gradual expansion from 0:00084 to 0-001 Paris inch. 
So soon as the cytoblasts have attained their full size, a 
delicate transparent vesicle rises upon their surface. This is 
the young cell, which at first represents a very flat segment of 
a sphere, the plane side of which is formed by the cytoblast, 
and the convex side by the young cell, which is placed upon 
it somewhat like a watch-glass upon a watch. In its natural 
medium it is distinguished almost by this circumstance alone, 
that the space between its convexity and the cytoblast is per- 
fectly clear and transparent, and probably filled with a watery 
fluid, and is bounded by the surrounding mucus-granules 
which have been aggregated together at its first formation, 
and are pressed back by its expansion, as I have endeavoured 
to represent it in plate XV, figs. 4, 5,6. But if these young 
cells be isolated, the mucus-granules may be almost entirely 
removed by shaking the stage. They cannot, however, be 
observed for any length of time, for in a few minutes they 
become completely dissolved in distilled water, leaving only 
the cytoblasts behind. The vesicle gradually expands and be- 
comes more consistent (fig. 1, 4), and, with the exception of the 
cytoblast, which always forms a portion of it, the wall now con- 
sists of gelatine. The entire cell then increases beyond the 
