88 
W. J. DOWSON, On two species of Heterosporium etc. 
Thus the inoculation of the 19 th December had been effective in this case, 
and the time between the inoculation and the appearance of spore-produc¬ 
ing organs was something less than twenty-eight days. 
The imbedded material fixed upon the 22 nd December was sectioned, 
and stained with safranin and gentian violet and with gentian violet and 
orange G.; but neither germinating spores nor mycelium were visible any¬ 
where. From this it was suspected that the fungus conidia took longer 
to germinate, and further, to penetrate the host tissues than they did 
when growing upon nutrient media in pure cultures. 
Experiment VI. 
On January 17 th 1912 two larger and stronger Dianthus plants in 
separate pots were placed under one large bell-jar and inoculated with 
spores taken from a petri-dish-culture on salep agar. This culture had 
been made upon the 4 th December 1911, so that the spores were about 
six weeks old. The leaves chosen were chiefly the lower ones upon those 
parts of the plants facing the observer; but one or two upper ones were 
also inoculated. These latter were young and small, and it was with 
considerable difficulty that a drop of water containing spores was lodged 
upon their surfaces. The leaves were marked with two parallel ink lines 
drawn across the leaf at right angles to the mid-rib. 
These lines marked the places and boundaries of the inoculations. 
The spores were applied in the same manner as before with a small 
paint brush. Several leaves were treated in this way, care being taken 
that only sound healthy leaves were used. The plants were kept under 
bell jars. 
On February 9 th 1912 the plants were examined. Upon many of 
the inoculated leaves small grey spots from 1—1,5 mm in diametre were 
seen. Some of these spots were cut out, and examined under the micro¬ 
scope; from others sections were cut which were killed and stained; the 
stains used being Bleu coton G4B, and the combination Fuchsin and 
Lichtgrün. These preparations showed mycelium to be present, and 
spores of H. echinulatum. Other pieces were also cut out, and fixed 
in dilute Flemming solution under the air pump for the purpose of im¬ 
bedding in paraffin, and obtaining microtome sections. 
On the 12 th February the plants were again examined. Definite 
spots could clearly be seen upon both old and new leaves. The spots 
possessed a diametre of from 1—3 mm, and were of a greyish green 
colour with a central portion of olive-green composed of bundles of conidia- 
bearing hyphae of H. echimilatum. The small spots, those namely of 
from 1—2 mm in diametre showed very small central portions which 
appeared as mere dots to the naked eye; the larger spots of 3 mm dia¬ 
metre showed centre spots of 1—2 mm diametre. As the grey spots 
were first seen upon the 9 th February, the fungus had taken twenty-three 
days from inoculation to reappearance; that is 23 days had elapsed from 
the sowing of spores to the time when spores were produced from the 
mycelium developed from the infecting spores. (Schluß folgt.) 
