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Only the young tender leaves can be infected by spores falling 

 directly upon them, the epidermis or skin of old leaves being too 

 tough for a germinating spore to penetrate. Old leaves, however, 

 are readily infected through a wound, such as might be caused by 

 the puncture of a " green fly " (aphis) or other insect or caterpillar. 



The white moulds, to which the fungus under consideration 

 belongs, produce two kinds of spores, those mentioned above being 

 known as summer spores. These are produced in enormous 

 numbers, and in rapid succession during the summer months. 

 Their special use is to enable the fungus to extend its area of 

 distribution at a rapid rate. The summer form of spore is always 

 the kind to produce an epidemic, or the rapid development and 

 extension of a disease. The second kind of spore, called a winter- 

 spore, is produced in quantity late in the season, when the host- 

 plant has ceased to grow for the year. These spores do not 

 germinate at once, but remain in an unchanged condition until the 

 following spring, when they germinate and infect the young foliage 

 of the host-plant 



Now it so happens that the mildew on Euonymus only produces 

 summer-spores in this country, and consequently cannot reproduce 

 itself the following season by means of winter-spores. However, 

 the white patches of mildew on the leaves retain their vitality 

 throughout the winter, and produce a crop of summer-spores the 

 following spring. These summer spores infect the young foliage, 

 and commence the epidemic anew. 



Preventive Measures. 



The chief point to keep in view is the fact that unless the 

 bushes are infected in the spring of each season there can be no 

 renewal of disease. 



Such infection depends on the presence of the fungus on the 

 leaves of the previous season. It might prove impracticable to 

 remove all such diseased leaves and to promptly burn them, but the 

 disease would be reduced in proportion to the number of badly 

 diseased leaves that were removed. 



Commencing about the middle of March, flowers of sulphur 

 should be dusted on diseased plants in warm places where the 

 sun shines on the bushes, or both diseased and healthy plants 

 should be sprayed with a solution of sulphide of potassium ( = liver of 

 sulphur), two ounces dissolved in three gallons of water. The 

 spraying should be repeated at intervals of ten days for the first two 

 months, and afterwards at intervals depending upon the con- 

 tinuance of the disease. 



If insects appear on the bushes they should be kept down by 

 means of an insecticide. 



Sir Daniel Morris, k.c.m.g., f.l.s., by whom the paper was 

 read in che absence of Mr. Massee, exhibited leaves of Euonymus 

 attacked by the mildew and added further information on the subject, 

 Euonymus japonicus was introduced to this country in 1804, and there 

 are several handsome variegated forms with gold and silver markings. 



