330 Blackman . — the Fertilization , Alternation of 
earlier observers they are of two kinds, thick-walled and thin-walled, the 
latter being found more usually in the interior of the mass ; it is possible, 
also, that there may be some connexion between the thickness of the 
wall and the time of year at which the spores are formed, for the first- 
formed spores seem to be almost all thick-walled 1 . 
Each cell of the teleutospore contains dense vacuolate cytoplasm 
with a quantity of yellow oily material which gives the colour to the spore. 
There is a single nucleus of considerable size with a chromatin network 
arranged superficially round the cavity and one or more small nucleoli 
(Figs. 14 and 15). The wall of the spores shows usually no clear distinction 
into layers. Near the septum, the wall of each cell (of the thick- walled 
spores) is thinner at one spot, and into the cavity so produced the 
protoplasm projects slightly (Fig. 14). It would seem that the wall is 
never thickened at these spots, for such thin places in the wall are found 
in comparatively young spores ; they are thus to be considered of the 
nature of pores. These pits are not to be found in the thin-walled spores 
(where they are obviously unnecessary), but the naturally thin wall may 
project slightly at the corresponding points. 
Germination . Under suitable conditions of moisture and temperature 
germination takes place very readily, in a moist atmosphere at 20° C. the 
promycelium being formed and the sporidia developed in less than three 
hours. The cytoplasm forces its way through the pore described above, 
and, after swelling out into a spherical mass, as in Phragmidium , attains 
a considerable length before the nucleus migrates into it (Fig. 16). The 
nucleus, very much constricted and condensed in its passage through the 
pore, takes up a position in the middle of the tube and is there to be seen 
as a narrow elongated body with a few small nucleoli, and granular 
chromatin which forms usually only an indistinct network. Under suitable 
conditions of air-supply the nucleus then proceeds to divide. 
Nuclear division. The first sign of division is the gathering of the 
granular chromatin material towards one end or the middle of the nucleus, 
while at the same time a small, deeply staining, spherical body, the 
centrosome, is to be observed in the cytoplasm and connected with the 
nucleus by a portion of slightly differentiated cytoplasm or kinoplasm 
(Fig. 1 7). The chromatin then forms a closely coiled spireme thread in 
the middle of the nuclear area and the outline of the nucleus becomes very 
faint (Fig. 18); the centrosome was not traced at this stage. The thread 
then becomes apparently broken up into a number of narrow, elongated 
1 The suggestion put forward by Kienitz-Gerloff (Bot. Zeit., xlvi, 1888, p. 388) and Dietel 
(Hedwigia, xxviii, 1889, p. 99), that the thin- walled spores represent in this genus the endospores, 
cannot be accepted. Both kinds of spores are uninucleate, and both are able to form normal 
sporidia ; the long, undivided tubes put out by the thin-walled spores were no doubt the result of 
special conditions of growth (see Blackman, 7 ). 
