DISEASES DUE TO FUNGI 75 
passes up into the stem. Here it is found solely in the 
woody parts. When the plant dies, the fungus leaves 
the vessels and, penetrating the cortex, forms at the base 
of the stem a white external growth (Fig. 14). This is 
the active fruiting stage, and the spores are readily 
blown about, enabling the fungus to spread rapidly. 
Occasionally the fungus may penetrate the fruit, causing 
a soft rot. Infection rarely takes place in the seed-boxes 
or pots, but almost entirely after the plants have been 
placed in the houses. 
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““Comet ” soft growth... |0-8 |12]| 6 | 4/4/20 
Do. do. .. |1:05|12] 8 | 4/4/20 
Do. do. .. | 1-20] 12 | 10 [18/4/20 
“Comet ” hard growth... |0-45;12 | 6 | 4/4/20 
Do. do. .. |o7 [12] 8 | 4/4/20 
Do. do. .. |0-75/12/ 10 [18/4/20 
“Comet ’ starved growth |0-45/12| 6 | 4/4/20 
The Causal Organism.—Verticiluum albo-atrum, to 
which this disease is due, produces its spores characteris- 
tically at the tips of short branches arranged in whorls or 
verticils around the main conidiophore. The spores, 
which are produced in quantity at the base of every 
plant killed by the fungus, are extremely light, and are 
readily blown about in the air. They settle upon the 
soil or plant debris and germinate, producing a white 
mass of hyphe. If sufficient food is available, the 
hyphe produce a crop of spores, and so infection is 
abundant. After a time the mass of hyphe produces 
innumerable small sclerotia or resting bodies, by means 
