On the Morphology and Development of Phoma Richardiae n. sp. 
247 
30 //. On the majority of media the mouth does not project, at most a 
mere rim round the edge being present. On Calla, however, a short 
distinct neck, notable in the earlier stages by reason of its dark colour, 
is usually present (Fig. 1, io , //). 
When ripe the wall, which consists of very irregular cells, is brown- 
black, or black. A number of loose liyphae are scattered over its surface; 
in some cases — notably in potato cultures — they are congregated 
around the mouth, while in others they radiate from the base. 
Very commonly two or more pycnidia fuse together, producing a 
compound fructification with more than one mouth. 
In a gar-cultures the pycnidia are formed in the aerial mycelium, 
on the surface of, and immersed in the agar. Spores are extruded even 
from those immersed. 
Temperature has considerable effect upon pycnidia formation. 
Cultures on plum agar kept at different temperatures yielded the following 
results: 
Temp. 
No. of pycnidia per area a 
Avge diarn. of pycnidia 
12° C 
1,5 
0,1 —0,15 mm 
19° C 
2 
0,1 —0,2 mm 
28° C 
14 
0,03—0,05 mm 
The culture kept at 28 0 C was remarkable in that pycnidia were 
formed immediately behind the growing points. At ordinary room tempe¬ 
ratures and below, this does not occur; during the growth of the culture 
a peripheral band of hypliae some 3 mm broad, as yet sterile, is always 
to be seen. 
3. Development of pycnidia. 
The immediate forerunner of a pycnidium is a solid mass Or prim- 
ordium, which may arise by one of two methods designated by von Tavel *) 
Symphyogen and Meristogen respectively. 
Symphyogen. Development of the primordium was followed by 
means of moist-chamber cultures. An agar drop was inoculated with 
spores of the fungus, and as soon as pycnidia began to develop — about 
48 hours later — a favourable one was selected and its position marked 
by a circle drawn on the cover glass. The young pycnidium was then 
observed every few hours and drawings made with the camera lucida. 
Hypliae in a particular part of the mycelium become closely woven 
together, branching profusely. Some of the branches remain short, while 
others grow out as vegetative hyphae, their bases only contributing to the 
interwoven mass (Fig. 1 , 12 , ij). In a short time all that can be seen 
is a great number of loosely woven hyphae surrounding a central tighter 
mass, which begins to assume a pseudoparenchymatic appearance (Fig. 1, 
14 ). At this stage, which, in the case of the first formed pycnidia occurs 
some 24 hours after formation commenced 1 2 ), groups of spores whose origin 
1) Vergleichende Morphologie der Pilze (Jena 1899, G. Fischer). 
2) The later formed pycnidia develop more slowly. 
