84 
W. J. Dowson, 
formation, however, heads hearing a chain of two spores besides one other 
spore can be observed. Exceptions, however, occur, and in one case a 
conidiophore head was seen to bear three spores besides a prolongation of 
the conidia-bearing-hypha (fig. 27 b). 
The conidia of both are cylindrical with hemispherical and not oval 
ends; those of H echinulatum are larger and longer in proportion than 
those of H. Betae ; and whereas the conidia of the latter are usually two- 
celled those of the former are generally four-celled. 
III. Infection Experiments. 
1. On Beta vulgaris with species of Heterosporium, Alter- 
naria and i Torinodendron, originally found upon diseased 
Beta leaves. 
For this purpose seeds of Beta vulgaris were sown in pots, five 
seeds to each pot. When the young seedlings had produced two foliage 
leaves besides the cotyledons, they were placed under bell jars, two pots 
being placed under each bell jar, and six pots being taken in all. The 
spores were obtained from petri-dish cultures on salep agar, and in the 
case of Alternaria and Hormodendron were brushed from off the conidia- 
bearing hyphae on to the agar surface by means of a little water and a 
fine paint brush. In the case of Heterosporium, however, owing to the 
great number of aerial hyphae the spores were obtained by means of a 
needle and placed in water; in this latter case some agar and hyphae 
came away with the needle. Another lot of spores was obtained in the 
same way but with a 5 % glucose solution instead of ordinary tap-water. 
It was known that the spores could germinate in ordinay tap-water; but 
that they did not form mycelia beyond a few straggling hyphae; in glu¬ 
cose solution, however, well-developed mycelia were found, and it was 
thought that these well-nourished mycelia might be able to infect the 
Betae leaves; de Bary 1 ) showed this to be possible with the ascospores of 
Peziza Sclerotiorum upon carrots and young seedlings of Petunia violacea, 
Zinnia elegans etc. The spores were brushed onto both sides of the foliage 
leaves with a small paint brush, so that under each bell-jar was one pot 
with plants inoculated with spores suspended in 5 °/ 0 glucose solution. 
In the case of Heterosporium, a little mycelium, and pieces of agar 
were present with the spores; the suspension was not filtered owing to 
the small number of spores of this fungus. On the 16 th October 1911 
the following inoculations were made: 
Experiment I. 
Only three plants in each pot were inoculated, the other two acted 
as controls. 
The plants were examined on the 30 th October 1911. All those 
plants inoculted with spores suspended in water did not seem to be in¬ 
fected. In one or two cases a little mycelium was removed by a needle 
1) de Bary, Botanische Zeitung 1886, p. 396—397. See also Brooks, F. T. 
Annals of Botany, 1908, p. 482. 
