86 
W. J. Dowson, 
From another pot three plants were selected which were yellow and 
wilted. The spores were taken from a petri-dish culture on salep agar 
and placed upon the leaves by means of a small paint brush and a little 
water. In the case of the plant with the severed mid-ribs, both the leaf 
blade and the cut portions were inoculated: 
1 plant, 3 leaves wounded, 
3 plants in low state of vitality. 
The plants were kept under bell-jars during the whole time. 
On 20 th January the 3 plants were found to have little growths 
of mould upon their surfaces. These growths upon examination proved 
to be Heterosporium. The growths were found upon parts of the plants 
which were evidently dead, the discoloration being dark brown; upon the 
yellow and wilted portions no fungus growth made its appearance. Sub¬ 
sequent microscopical investigation upon the wounded and inoculated leaves 
showed that the spores had indeed germinated (see fig. 46), and had 
produced small mycelia which ramified over dead tissue at the edge of 
the torn mid-rib. In one or two instances the hyphae had entered the 
stomata of this dead tissue. 
Good preparations were obtained by treating portions cut out of 
the leaves and including the torn place, with lactophenol and staining in 
Bleu coton G4B 1 ). The cells of the healthy tissue took up the blue stain, 
but those of the dead tissue did not, and remained almost transparent, 
while the hyphae of the fungus were stained a deep blue. By this means 
it was easy to trace the course of the hyphae which appeared as blue 
threads upon a transparent area of dead tissue surrounded by healthy 
tissue stained light blue. In no case were hyphae observed among the 
cells of the healthy tissue. It was concluded from this that the Hetero¬ 
sporium under the conditions of the experiment behaved purely as a 
saprophyte. 
< 
Experiment IV. 
In March 1912 it was decided to try inoculation experiments with 
the Heterosporium upon starved Beta plants. For this purpose plants 
were selected from a number planted during the previous autumn which 
were now a fair size, the leaves having attained a length of six or seven 
inches. Ten plants were taken and replanted into two pots in sand and 
were kept under a bell-jar for three weeks without water. At the end 
of this time there was no visible difference between these plants and 
those growing in earth and not kept under bell-jars. On examination it 
was found, however, that the leaves of the starved plants were thinner 
and more delicate than those kept under normal conditions. The two 
pots were then left over night in a warm room; the following morning 
the plants were found to be complete’y wilted, all the leaves had become 
flaccid, and were hanging over the edges of the pots. After standing in 
the cold house for a few days they partially recovered, the youngest 
leaves became once more turgescent, while the older and outer ones 
remained more or less wilted, but were by no means dried up. On 19 th 
1) See Klebahn (3), p. 23. 
