468 
JOHN A. ELLIOTT 
does not fall off, the conidiophore may bud again at the side of the 
swollen end and produce a second short "joint" which bears a second 
spore. This process, repeated, causes the geniculation which is some- 
times given as a specific character. Branching occurred occasionally 
in all the species but was not often observed under natural conditions. 
The width of the conidiophores was quite constant. Constriction 
differs between species and with the age of the conidiophore. In 
some species no constriction was noted while in others the constriction 
was marked. 
Color is as distinctive of the conidiophores as of the spores and is 
usually concolorous with that of the spores. The only variations in 
the color of conidiophores on artificial media corresponded with the 
color change of spores. 
3. Aerial mycelium: Parasitic species under usual conditions pro- 
duce little or no aerial mycelium. Under humid conditions, a very 
little aerial mycelium was sometimes produced by some species. This 
was always lax and white, and although in some species it was thicker 
in cross section than in others, it was so nearly featureless as to be 
thought worthless in classification. More or less aerial mycelium 
was produced by all species under some conditions of artificial culture. 
In some species, notably A. brassicae var. microspora and M. sarcinae- 
forme, it could be found only with the microscope. Other species 
produced aerial mycelium in abundance under humid conditions on 
rich media. 
4. Submerged mycelium: The characters of the submerged myce- 
lium were the most variable of all characters studied. Under ordinary 
cultural conditions on standard media the mycelium of some species 
had distinguishing characteristics, but any change in the cultural con- 
ditions might bring about a change in the characters of the mycelium 
which would make its identity doubtful. On low-grade nutrient agar 
the mycelium of most species was colorless and, with a few exceptions, 
characterless. On some media the color, width, and general character 
might separate certain species from certain other species, but under 
the influence of strong inhibition, such as was brought about by bac- 
terial influence, the changes entirely destroyed any distinguishing 
characters. In most cases age greatly affected the mycelium in color, 
septation, and constriction. 
