Ve eC UO 
— 
° 
-_—~ 
Ree kyo) MROMLON: OF 
§ 
VEGETABLE PATHOLOGY, | 8389 
eee : 
cases, but, as we have already seen, they are not essential to its per- 
petuation from one year to another. They are narrowly ovoid in 
shape, being more pointed below, and are divided into two cells by 
a transverse septum near the middle.* 
Conidia-bearing stalks similar to those we have already described 
often grow in great numbers from the outer wall of the perithecium 
around the ostiolum, and like developments have been observed by 
us arising from similar parts of the spermogonia. These stalks pro- 
duce conidia in every way like those which are formed in the early 
stages of the disease. By placing the old diseased leaves, upon which 
there are perithecia, in a moist atmosphere under a tumbler or bell 
jar the conidia-bearing stalks and conidia will grow from the latter 
in the greatest profusion. : 
From our studies of this fungus we conclude that its life history is 
limited to the developments above described: First, there is the 
mycelium, which endures throughout the year; second, the conidia, 
produced in the summer on short stalks arising from cushion-like 
masses of mycelium formed just beneath the cuticle. This stage ap- 
ears to us to correspond to the pycnidial stage of the fungus of the 
Riahe-wot of grapes, only, in this instance, the pycnidial walls are not 
developed, consequently the basidia and their spores are exposed; 
third, the spermagonia, which appear late in the season; and, fourth, 
the perithecia, with their asci and ascospores, found in early spring 
on leaves destroyed by the blight the previous year. Thespore-forms 
are the summer conidia, the conidia which are produced on stalks 
_ that grow from the tops of the spermagonia and perithecia, the sper- 
matia, and the ascospores. 
The conidia are designed for the rapid propagation of the fungus, 
as shown by their great abundance and the ease with which they 
germinate. The ascospores, securely protected by the walls of the 
«perithecium, are doubtless designed to perpetuate the fungus under 
conditions fatal to the life of the conidia. 
(f) TREATMENT. 
* 
A knowledge of the habits of the fungus of Strawberry-leaf Blight 
shows us that the treatment of the disease must be preventive. The 
fungus, when once inside the leaf, can only be destroyed at the ex- 
pense of the latter. 
We can mitigate the evil and oftentimes wholly avoid it by pursu- 
ing special systems of culture. By annually renewing the settings 
and planting only in deep and thoroughly well drained soil loss from 
blight will séldom occur. Some have escaped the ravages of the 
disease by removing all the old leaves immediately after the fruit is 
harvested and cultivating the ground, at the same time adding some 
quick fertilizer. The easiest way to remove the leaves is to mow the 
beds, then rake the leaves together and burn them. 
A simpler line of treatment, and one more likely to secure the de- , 
sired result, is the application to the plants of some fungicide which 
will destroy or prevent the germination of the conidia falling upon 
the leaves. We have seen from our laboratory experiments, that 
these conidia will not germinate in very dilute solutions of hypo- 
sulphite of soda or sulphate of copper. It is asimple matter to apply ~ 
similar solutions tothe plants in the field, where it is only reasonable 
* These ascospores are more elongated and rather more pointed at the narrow end 
than those figured by Tulasne, but they are certainly of the same species. 
