On two species of Heterosporium particularly Hetcrosporium echinulatum \ 41 
V. The occurrence of the disease and the winter cultivation 
of carnations. 
The disease makes its appearance in the late autumn during and 
after periods of damp. If the weather remains dry with little rain, the 
disease may not appear much before winter; on the other hand if the 
weather has been at all wet and the atmosphere consequently kept damp 
for some time, the carnations will be noticeably infected in the early 
autumn. In fact seasonal and climatic conditions seem to play a great 
part in the degree and extent of the outbreak. During any period of 
damp at any time of the year some spots of H. echinulatum may be 
found upon the lower leaves of the carnations, but the disease is always 
very much more pronounced during the winter months, and is scarcely 
to be noticed during the summer. During wet summers the disease spots 
are more frequently met with than during dry ones, and in dry winters 
the carnations are less affected than in wet winters. 
The spots at first appear no bigger than pin-points, and are grey in 
colour. The tissue both of the spot and of the surrounding portion is 
not sunk or shrivelled in any way. They are only to be made out upon 
one side of the leaf; in the case of the infection experiments they only 
appeared upon the upper surface. After a few days, however, the spots 
have increased in area, and when thay have attained a diametre of 
1—2 mm, they are plainly visible on both sides of the leaf, indicating 
that the parasitic hyphae have spread from one surface of the leaf to the 
other. In the middle of each spot is to be seen a scanty aerial myce¬ 
lium, composed of long wavy hyphae, which are for the most part spirally 
coiled. This aerial mycelium appears upon both sides of the leaf. Coni- 
diophores begin to appear when the disease spot has attained a diametre 
of between 2 and 3 mm, and are dark olive green in colour, and 
dispersed among the central patch of aerial hyphae. The spot increases 
in size until it extends from one margin to the other. The conidiophores 
are arranged in fairly regular concentric circles around the first central 
patch. Very often cases were seen in which two fairly complete circles 
of conidiophores were produced upon the disease patches, but no spots 
were seen with conidiophores quite so regularly arranged as would appear 
to be the case from Rostrup’s figure. 
Cuttings made in late summer for next year’s plants were also 
sometimes found to be infected, although at the time of cutting, the 
plants appeared quite free from the disease. During the winter months 
some of these young cuttings are found to be diseased. The spotted 
leaves of these are removed whenever they are found. 
In any given bed of carnation plants which are always grown nearly 
touching each other, whether of old plants or of cuttings, a few are 
always present which are infected with FI. echinulatum. The parasite 
may be in the stage of infection, or between that and the production of 
spores, or may have actually produced spore-bearing disease patches. 
The material for infection always seems to be present and as many of 
the lower leaves of the carnations plants can be easily wetted, the trans¬ 
mission of the disease from one leaf to another and from one plant to 
another by means of wind and rain can be thus accounted for. It was 
found in the infection experiments that it was possible to lodge a drop 
