3 1 8 Wager. — On the Structure and 
I have often found portions of the stem, very much hyper- 
trophied, but with few or no basidia and gonidangia, to 
contain them in abundance. One may look for sexual organs 
in vain in some localities and find them plentifully in others, 
and one may find them in stems the surface of which is 
almost completely covered with the asexual reproductive 
organs of Percnospora pai'asitica. They may be accompanied 
by much hypertrophy or by very little, with many asexual 
organs or with very few. I have generally found it a pretty 
certain indication of the presence of sexual organs if the 
portion of the stem on which they are suspected to occur is 
brittle, and easily broken when slightly bent. Where they 
do not occur the stem may be bent double before it breaks. 
In cutting sections by hand, one is also able to judge fairly 
easily whether sexual organs are present or not. When 
present, the sections come off beautifully smoothly, and 
without the least suspicion of tearing or toughness ; but if not 
present, there is a larger resistance to be overcome, and 
unless the razor be in good condition a certain amount of 
tearing is the result. Generally speaking the sexual organs 
are to be found more easily towards the end of the season 
than at the beginning. 
In many cases, and perhaps in the most favourable con- 
dition for observation as a rule, that part of the stem in which 
they are to be found in the early stages of their development 
is coloured a dark reddish purple and is somewhat swollen. 
When the oospores are mature, the stem becomes brown and 
rotten, and the tissues almost completely broken up. In the 
earlier stages of their formation, although they may be found 
in great abundance in some parts of the stem, there is no 
apparent degeneration visible in the cells of the host-plant 
such as appears later. The cells contain protoplasm, nuclei, 
and chlorophyll grains, and present a normal appearance, 
except for the presence of haustoria which are to be found 
lining the cell-wall in some cells in considerable numbers. 
Peglion (’93) has given a very careful account of the action of 
the fungus upon the tissues of the host-plant. 
