12 
W. J. Dowson, 
a lessening in the diameter of the projecting hyphae (fig. 6). In some 
cases these aerial hyphae had reached a considerable length (fig. 7), and 
were studded with minute water drops, so much so that it was not at 
all easy to make out the septa (fig. 9). These, however, as could be seen 
in favourable cases, were numerous, and closer together than in the 
buried hyphae (fig. 9). Very often in an old culture in which the agar 
had dried somewhat, and had contracted or had been used up by the 
fungus, the junction of the conidiophores with the nourishing mycelium 
was very noticeable. The thinner conidiophores arose almost direct from 
the thicker basal portion which was formerly buried (fig. 6). 
The spores and spore-bearing-branches were formed at night. 
a 
3. Development of the conidiophores. 
On the 10 th Jan. 1912 observations were made upon a young colony 
sown on the 6 th inst. Young conidiophores were seen all around the cir¬ 
cumference of 
the colony; but 
judging from 
their length, 
and comparing 
them with those 
of colonies 2 
days older; it 
was thought 
that these 
would not form 
spores during 
the night; this 
proved to be 
correct. How¬ 
ever, where the 
colony came in 
contact with 
water and air 
at one edge of 
the agar drop, 
one hypha of 
the mycelium 
was seen bea¬ 
ring much lon- 
conidial 
Figs. 11—24: Heterosporium Betae (x 215). 
Distal portion of conidia-bearing-hyphae, showing 
ger 
Fig. 11: 
swollen head of the conidiophore. a and b : from hanging-drop- branches, two 
cultures, c and d : from diseased Beta leaf ( c x 600). — 12: Portion Qr 0 f 
of mycelium from a hanging-drop culture. — 13—16: Origin and r i • i i 
development of the conidia. — 17—24: Various forms of the co- wnicil 001 e one 
nidiophore; for explanation sec text. (Drawn without the help of spore at their 
the drawing apparatus.) tips (see fig. 13). 
The spore was 
joined to the swollen head of the conidiophore by a definite stalk, which 
was quite colourless and transparent, while the conidiophore was greyish, 
and. the spore a chestnut brown. A drawing was made at this stage at 
