THE MAPLE DISEASE (RHYTISMA ACERINUM.) 101 
In the two last cases, Rhytisma appeared after two months and a 
half. The patches were at first white and greenish-grey, then 
turned partially, and at last entirely black ; by the middle of July 
the patch was completely formed. 
These plants were shown to M. Brongniart, M. Duchartre, M. 
Roze, and several other botanists. The leaves, which had all 
fallen, were gathered in the autumn. The parasite did not appear 
the next year, or subsequently ; it must, therefore, be annual. It 
does not seem to spread. Of the plants experimented upon, 
merely the- lower leaves, which were the only ones developed at the 
time of the experiment, were spotted ; the spots were all in the 
same state ; the mycelium did not spread. 
In 1876 I endeavoured to trace on the leaves when they had 
attained their complete size, lines and crosses by means of the 
Rhytisma. The spots began to show, but the tissue dried up in all 
the leaves ; the parasite was very incompletely developed, and did 
not re-appear the following year. So the fungus is altogether con- 
fined to the deciduous foliaceous organs ; it is only fully developed 
on the organs when they are in a young state. 
It appears, then, in order to destroy Rhytisma , that it is enough 
to remove all the spotted leaves which fall in autumn ; that is, 
supposing that the corpuscles ( speimnatia of M. Tulasne), which 
are produced in enormous numbers on the living leaves ( Xyloma ), 
cannot reproduce the parasite. 
The red spots on Plumtrees, produced by Polystigma rubrum , an 
ascomycetous fungus of quite another group, and much more 
dangerous, have probably an analogous life history. 
CALIFORNIAN FUNGI. 
By M. C. Cooke. 
The following few remaining numbers of a collection made by 
Dr. Harkness are supplementary to our previous record : — 
Hydnum Stevensoni. B. Br. 
On Oreodaphne. Sierra Nevada. No. 1073. 
No. 1044, on oak, seems scarcely distinct. 
Irpex paradoxus. Fr. 
On Oreodaphne. Sierra Nevada. No. 1047. 
Stereum muscigenum. B. $ Br. 
On Locust bark. Sierra Nevada. No. 1060. 
Corticium. sp. 
On decaying culms. No. 1042. 
Not sufficient to determine ; the white species are numerous, 
and closely allied, so that without the margin little certainty can be 
assured. 
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