Sporangial discharge in Pilobolus. A. H.R. Buller. 61 
18-22 x 6-8, not turning blue with iodine. Spores hyaline, 
oblong elliptical, rounded at both ends, 4-6 x 2-2°5 pw, agglu- 
tinated together in clusters of eight. Paraphyses hyaline, sparse, 
narrowly cylindrical or filamentous, 12-16 x 1-5-2. Basal 
hyphae hyaline, 2-4 in diam. sparsely septate. On bark of Pinus 
sylvestris, Weybridge, Surrey, Mr A. A. Pearson, 22nd November, 
1920. This is a very interesting addition to the British Fungus 
Flora, because it represents the Inoperculeae immarginatae 
group of Discomycetae hitherto unknown in Britain. 
UPON THE OCELLUS FUNCTION OF THE 
SUBSPORANGIAL SWELLING OF 
PILOBOLUS. 
By Professor A. H. R. Buller, D.Sc., Ph.D., F.R.S.C. 
As is well known, the sporangiophore of Pilobolus shoots 
away its sporangium to a distance of several feet and therefore 
acts as a gun. The gun consists of three parts: (1) a basal 
reservoir which is at first densely filled with protoplasm and 
which, with the aid of rhizoids, serves to fix the gun firmly to 
the substratum, (2) a slender cylindrical stipe several milli- 
metres long, and (3) a large oval subsporangial swelling. The 
shape of the stipe and of the subsporangial swelling is like that 
of an inverted Florence flask. The projectile—the sporangium— 
is seated on the free end of the subsporangial swelling, is dis- 
coid, is covered with an intensely black membrane, and contains 
many thousands of spores. Pilobolus Kleinii and P. longipes 
can both shoot their largest sporangia vertically upwards to a 
maximum height just exceeding six feet and to a maximum 
horizontal distance just exceeding eight feet. 
When discharge of a sporangium takes place, the neck of the 
subsporangial swelling just beneath the sporangium is ruptured 
transversely, the wall of the swelling and of the stipe contracts 
elastically, and the cell sap is squirted out of the top of the 
swelling so that the sap carries the sporangium with it through 
the air. Hitherto, the swelling has been supposed to function 
merely as part of a squirting apparatus. 
The subsporangial swelling of Pilobolus functions not merely 
as part of a squirting apparatus but also as an ocellus which 
receives the heliotropic stimulus which causes the stipe to turn 
the fungus gun toward the light. The swelling is transparent 
and refracts light like the bulb of a Florence flask filled with 
water. Its diameter is always greater than that of the black 
sporangium which it supports. 
