On the Morphology and Development of Phoma Richardiae n. sp. 
327 
It has already been noted that the production of mycelial gemmae, 
brown conidia, and “spore gemmae“ was more marked on plum agar 
— which is acid — than on Salep, which is neutral. It seemed likely, 
therefore, that the use of media acidified with various substances might 
yield results of interest. Of the few substances tried up to the present, 
only one — Oxalic acid — has given any noteworthy result. Using 
0,5° o acid in 5% gelatine, germination and subsequent growth were slow, 
but otherwise normal. With 1 % acid the results were rather variable, 
due no doubt to the fact that the gelatine would not dissolve all the 
acid 1 ). Sometimes growth was normal; more commonly it was very slow 
and the cells were greatly swollen and distorted. Young plants were 
produced exactly like those produced from spores extruded on old cultures, 
e. g. Casein gelatine (Fig. 6 . j— 7 , comp. Fig. 6 , /— 4 ). The rate of growth 
gradually quickened, and the hyphae became more normal, possibly due 
to the deposition of crystals of acid, thus freeing the gelatine of a pro¬ 
portion hitherto dissolved. Occasionally the transition from slow distorted 
growth to normal was quite rapid (Fig. 6 , 6 ). Similar, but more regular 
results were obtained with plum agar acidified with Oxalic acid; in this 
case the slow distorted growth was maintained. 
Though no development of the characteristic brown colouration has 
been produced on artificially poisoned media, it is nevertheless interesting 
to find that the form of the hyphae may be so similar to that on old 
cultures. The results of the experiments with Oxalic acid are sufficient 
to justify further trials, on a larger scale, and these I hope to carry out 
in the near future. 
In the course of a few trials designed to test the effect of tempera¬ 
ture on reproduction, the fungus was cultivated at 34° C. As might have 
been expected with a species whose form is so variable, the growth was 
greatly modified at this high temperature. Not only was development 
very slow, but the plants consisted of remarkably distorted hyphae (Fig. 6 , 
8 — 10). 
9. Infection Experiments. 
Infection experiments on Richardia africana have yielded uniformly 
negative results. Healthy plants, plants which had been kept for a month 
in a state of drought, and in a water logged soil in a damp atmosphere 
respectively, and plants etiolated by a fortnight’s darkness were all 
inoculated with no result. Following injury of leaves by a knife, by 
singeing and by treatment with steam, the fungus obtained a hold on the 
area actually killed, but did not penetrate into living tissue. 
A considerable number of decaying Calla leaves from different 
districts have been examined in the course of this investigation, but only 
in the one case have P^^^-pycnidia been met with. There is little 
doubt therefore that the fungus is saprophytic only on Calla. 
1) The gelatine was made first, powdered acid to the required amount being then 
added. In hanging drops the amount of suspended acid appeared to vary slightly. 
When the acid is first dissolved in water and the gelatine then added, a part of the 
former is thrown out of solution. Had the medium been made in this way the 
results would probably have been more even, as the acid crystals in this case are finer 
than the particles obtained by grinding. 
