308 FUNGOUS DISEASES OF PLANTS 



of Bordeaux mixture, so that the ordinary strength may be used 

 without causing any trouble. In the case of the early sprayings 

 in the spring when there is apt to be cold weather, it has been 

 found that plants will sometimes be injured by the Bordeaux. If 

 care is taken not to apply the mixture just before a hard freeze, 

 little trouble will result. 



Alternaria Violae Gall. & Dorsett 1 produces a leaf spot of violets 

 in the greenhouse, particularly when the houses are not well regu- 

 lated with respect to dryness or moisture of the air, heat and cold, 



FIG. 140. LEAF SPOT OF BEETS; A FIELD OF SUGAR BEETS BADLY DISEASED 



or when the stock is not in condition for vigorous growth. The 

 old spots, as in the case of most violet leaf diseases, are white, 

 although at the outset the spot is dark, and on the stem (which is 

 sometimes affected) the darkened areas are often persistent. 



Alternaria Brassicae (Berk.) Sacc. This species is not uncom- 

 mon upon cabbage and horse radish in Europe and America. It 

 produces brown spots with concentric markings. 



1 Dorsett, P. H. Spot Disease of the Violet. Div. Veg. Phys. and Path., U. S. 

 Dept. Agl. Built 23 : 1-16. pis. 7-7. 1900. 



