Wormald. — Further Studies of the ■ Brozvn Rot ’ Fungi. /. 309 
a canker was first cleansed by wiping it with cotton-wool moistened with 
95 per cent, alcohol; transverse sections were then made through the 
cankered portion and the sections placed in sterile water in a flamed watch- 
glass. 1 As a further precaution against contamination the outer layers of 
the bark were teased away with flamed needles, and particles of the internal 
brown tissues (bark and wood) were removed to a second watch-glass of 
water, from which they were transferred to carrot agar or prune agar in 
Petri dishes. In such plates, kept at room temperature (about 18 0 C.), the 
hyphae grew out readily and within six days had given rise to discs of 
mycelium 21 to 2*5 cm. in diameter; at this stage further primary growth 
was checked, but fan-shaped lobes appeared at certain points on the margin, 
and these gave rise to a zone of mycelium around the primary growth, and 
later another zone developed in a similar way (Plate XIV, Fig. 13). This mode 
of growth in agar plates is also shown by cultures of Sclerotiniacinerea when 
obtained directly from ascospores, and, as pointed out in previous papers, 2 
is a character which distinguishes this fungus, as found in Britain, not only 
from X. frtictigena , but also from the Brown Rot fungus which is common 
in America. 
Cultures obtained in this way in June and July were almost invariably 
pure, so far as could be seen. For further experimental work it was con- 
sidered desirable, however, to obtain cultures derived from single conidia. 
The agar-plate cultures were quite barren, but on transferring a little of the 
mycelium to sterilized potato in tubes, grey tufts of conidiophores with their 
chains of conidia appeared within a week. Conidia taken from the cultures 
on potato were isolated 3 on agar plates and the resulting ‘ sporelings 5 gave 
pure line cultures. 
In winter pure line cultures were obtained direct from conidia taken 
from a canker ; in general habit such cultures resembled those obtained 
from the barren mycelium of the young cankers. 
The cultures of the Shoot- Wilt fungus on sterilized potato were typical 
of Sclerotinia cinerea f. pruni , conidia being produced more freely than is 
the case in potato cultures of X. cinerea f. mali. These conidia were larger 
than the ‘ winter conidia ’ produced on the cankers, and were of the same 
order as those produced on the leaves and fruit in summer, the average size 
being approximately 17x12 y. 
1 Two watch-glasses were sterilized simultaneously, by passing them several times through 
a Bunsen flame, and left to cool with one inverted over the other to eliminate as far as possible 
contamination by the entrance of spores floating in the air. 
2 Ann..Bot., xxxiv, p. 164; xxxv, 1921, p. 129. 
3 For details of the method adopted by the author when isolating Monilia conidia on agar 
plates see Ann. Bot., xxxiii, pp. 371-2. 
