Notes. 269 
differ from mine, and to describe the naked-eye appearance of the 
infected plants. 
After the plant has already been weakened by the Peronospora , the 
Macrosporium makes its appearance as patches of a dense black 
colour and velvety appearance. The patches gradually spread, forming 
belts an inch or more in width round the leaf. This dense black 
appearance is followed by a fluffy white growth, which stands out 
from the leaf for the distance of one-tenth of an inch. This is caused 
by the hyphae which grow out of the multicellular spores. Whilst the 
Macrosporium is growing, the leaf continues to rot ; it does not shrivel 
and dry up as it does when attacked only by the Peronospora , but the 
plant retains a great deal of moisture, is very slimy, and gives rise to 
a most offensive smell. 
The specimens of the fungus which I examined in Bermuda con- 
sisted of a fine mycelium, which ramified through all the superficial 
tissues of the onion-leaf. The mycelium was septate, consisting of 
numerous elongated cells with granular contents. The cells occa- 
sionally branched, and frequently gave off fertile hyphae. It was 
noticeable that the hyphae ramified through the cells of the host and not 
between them , in marked contrast to the Peronospora. The fertile 
hyphae always bored their way to the surface through the outer cell- 
wall of the epidermis, their apices apparently exerting some solvent 
action on the cellulose. I do not remember ever having seen the 
hyphae projecting through the mouth of the stomata, as Mr. Kingo 
Miyabe describes, though it was not uncommon to find these hyphae 
growing through the guard-cells. 
The description of these hyphae given by Mr. Kingo Miyabe 
appears to me to be very accurate, but the spores borne at their ends 
consisted, in the species examined at Bermuda, of many more cells 
than those described in the paper above-mentioned. Twelve or more 
cells were not unfrequently seen in the larger spores, for they varied 
greatly in size ; and from each of these, hyphae grew out, which, by 
their branching and interlacing, form the white fluff described above. 
These hyphae often have secondary spores at the ends of the branches 
as described by Mr. Kingo Miyabe from his water-cultures. 
In an appendix to this paper Professor Fallow states that the in- 
vestigation of which it treats was undertaken with a view of determining 
‘ whether the Macrosporium was merely a fungus which had attacked 
plants previously suffering from Peronospora , as most botanists would 
suppose, or whether it might not of itself cause a disease of onions/ 
