118 Transactions British Mycological Society. 
2. Hyphae. 
The hyphae are uniform in size and appearance in all strains, 
varying from 3-7 in diameter, and are septate at short 
intervals. In colour they vary from hyaline to almost black, 
according to age and strain. The length of time taken by the 
hyphae to turn dark olive varies with the strain, some, e.g. 
strain S, taking a very short time, others, e.g. Z, taking much 
longer. This influences the macroscopic appearance of the 
colonies, those of S being dark almost to the extreme edge of 
the colony, while those of Z show a distinct light margin of 
varying width. 
Some strains, particularly Z, 60, 119A, when grown on Dox’s 
medium, show fine, hyaline hyphae coiled in a peculiar manner. 
These arise as lateral branches of the normal hyphae. Other 
strains do not show this peculiarity. 
3. Comdiophores. 
The conidiophores arise as branches from the vegetative 
hyphae and grow erect into the air. They are septate and 
usually dark in colour, though in some strains they are com- 
paratively light. 
The present strains can be grouped into three classes, ac- 
cording to the length of the conidiophores, thus: 
(a) Short conidiophores (less than 100 ~)—Z, 43, 108A, etc. 
(6) Medium - (100-250 2) —44. 
(c) Long yi (over 250 p) —S, IIo. 
These classes are arbitrary and all gradations occur between 
the shortest and longest. This classification is based on a series 
of cultures in Petri dishes, on potato agar in the light at labo- 
ratory temperature. The width of the conidiophore is approxi- 
mately that of the hyphae from which it arises. 
The differentiation of the conidiophores from the vegetative 
mycelium varies in different strains. In S, the conidiophores 
are very distinct from the mycelium, whereas in Z the conidio- 
phores are not differentiated. This distinction is more marked 
in those strains with long, unbranched conidiophores. In some 
strains the sterile part of the conidiophore is much branched, 
thus resembling the vegetative mycelium. In strain S the 
conidiophores are invariably unbranched, except at the apex 
where the head of conidia is formed. 
4. Formation of Conidia. 
The tip of the conidiophore is cut off by a wall to form the 
first conidium, this being invariably of the large type. The cell 
of the conidiophore immediately behind the first conidium may 
or may not grow out to form a second conidium, lateral to the 
