128 PICTORIAL PRACTICAL CARNATION GROWING. 
Carnation. The fruiting threads are very regular, pale olive in 
colour. They form little tufts, each thread being simple or branched, 
with very short branches, sometimes only like knots or nodules, the 
upper knots, as well as the apex of the thread, bearing the spores or 
conidia. These are cylindrical, with two to five transverse divisions, 
mostly two or three, externally rough with minute warts, slightly 
coloured. The conidia are capable of germinating from each one of 
the separate cells. The conidia at maturity may break to pieces, 
each producing a germinal tube capable of reproducing the disease, 
either by directly piercing the cuticle of the Carnation leaf, or by 
forming a dark coloured secondary spore at the tip of the branched 
germ tube. It thus has “ two strings to the bow” for reproduction. 
The secondary spores, being light and smooth, are probably capable 
of distribution over wider areas than the warted spores. Probably 
the latter hibernate during the winter out of doors; the warted 
spores certainly hibernate in greenhouses, although among Carna- 
tions and in favourable conditions for germination, they keep on 
reproducing and infecting new centres. 
In dying leaves numerous minute sclerotia are said to be formed, 
which remain as resting spores during the winter, and in the follow- 
ing season they produce conidia, which on Carnation leaves give 
origin to the first patches of disease. 
The consensus of opinion amongst practical gardeners is that a 
damp and stagnant atmosphere, sodden or unsuitable soil, a severe 
check or chill, and overcrowding the plants, all conduce to the 
attacks of Heterosporium (formerly Helminthosporium) echinulatum. 
The fungus is certainly developed rapidly under any and all of these 
conditions, especially that ot a damp and stagnant atmosphere ; 
hence, in the case of plants in pots, it is all important to give them 
as much light and air as possible, keeping them as dry as is consistent 
with safety, both at the roots and in the atmosphere. When plants 
are grown under glass the foliage should be kept as free from 
moisture as possible, for if the surface is dry floating spores alighting 
on the leaves do not germinate. 
Spraying with potassium sulphide, 1 oz. being dissolved in 1 quart 
of hot water, and when thoroughly dissolved diluted to 3 gallons 
FUNGOID ENEMIES. FIG. 62 (NEXT PAGE).—CARNATION MACROSPORE. 
N,a plant affected with macrospore, Macrosporium nobile: f, stumps of 
shortened leaves at layering; g, side growths; /, disease spots on the 
leaves; i, disease spots on the stem. 
O, a portion of a plant showing the partial result of fungus infection : 
Jj, stem pale above and about the diseased spots, the tissue ultimately 
shrinking, and the dark coloured spots or fruits of the fungus appearing 
on the destroyed paits; /, spots on the leaves; /, spots that have 
become confluent, and are causing the leaves to wither at the extremities, 
at first almost white, but becoming brown and shrivelled. 
P, three conidia of the fungus: m, pedicel; ”, a conidium, 
Q, a conidium germinating: 9, germ tube. 
