176 Barker . — The Morphology and Development of 
of the earlier branches is easily traced. Later, however, the 
hyphae begin to swell, and become more transparent, and, after 
further growth in length and branching have ceased, the 
individual hyphae are very indistinctly seen, and the system 
could not be correctly figured if the development from a very 
early stage were not followed. Further swelling and, at the 
same time, flattening out render them, except in a few cases 
here and there, almost invisible. A large number of oil drops 
also appear, gradually increasing in size. Later still, after the 
protoplasmic contents seem to have entirely degenerated and 
to have disappeared, they appear as nothing more than 
flattened walls (see Fig. 13, a-c). 
At this stage the fructification has acquired a brownish 
colour, due no doubt to these degenerated hyphae. 
While all these changes have been taking place, important 
developments of the central cell have occurred. These can 
be seen but indistinctly owing to the obscuring effect of the 
investing hyphae, particularly about the period of swelling up 
and flattening of those structures. At the time of the forma- 
tion of the first investing hypha, the central cell is compara- 
tively small, although as has been stated above, swelling has 
already begun to occur. The swelling continues during the 
formation of the hyphae, to such an extent that the whole 
fructification becomes a conspicuous and comparatively large 
body. By this time the contents of the antheridial branch 
and the ‘ trichogyne cell ’ have become disorganized and 
eventually disappear. At the same time those two structures 
have swollen considerably, and the fusion between them is 
then very easily seen. Later, their walls collapse, and in 
most cases all traces of their existence are lost (see 
Fig. 13, a , b , c). 
When the growth of the investing hyphae has ceased the 
central cell can still be seen, although with difficulty. Its 
outlines are no longer sharply marked ; but here and there 
portions of its surface can be sharply focussed, where the 
absence of investing hyphae has left it exposed. Later, when 
the hyphae begin to swell and become flattened out, such 
