10 



plants to freeze, however. By this treatment the plants are given a 

 rest, which is believed b}- many to be necessary to strong, vigorous 

 growth. While growers generallj" admit that slightly better results 

 are usuall}" obtained b}' this treatment than b}- the one generally prac- 

 ticed, the}' are, as a rule, of the opinion that the benefits derived will 

 not justify the expense necessary to carry the young plants through 

 the winter in good condition for spring planting. This is an impor- 

 tant problem, the practical solution of which would no doubt prove of 

 great value to all interested in the cultivation of the violet. We have 

 this work under way at the present time, and hope in a few years to 

 obtain some interesting results. 



IMPROPER SOIL CONDITIONS. 



Other writers claim that the disease is due to improper soil condi- 

 tions. The soil is either too heav}^ or too light in texture, and as a 

 consequence holds, or gives up. too much or too little moisture, or con- 

 tains too much or too little plant food. They advise selecting soil 

 suited in every wa}^ to the best growth and development of the plants. 



Since good soil is one of the prime factors governing strong, vigor- 

 ous, health}' plant growth, their advice is good, but extremely difficult 

 to follow. The question of securing proper soil is one of the most 

 perplexing with which the grower has to contend, requiring judgment 

 that can be gained only by many years of practical experience. 



IMPROPER CONDITIONS FURNISHED THE PLANTS DURING THE GROWING AND FLOWERING 



SEASON. 



Still others attribute the disease to improper methods employed 

 during the growth of the plants, such as growing them in the open 

 field, where they are exposed to drought, rains, dews, and the direct 

 rays of the sun during the summer, and lack of attention to properly 

 heating, ventilating, and fumigating the houses and to cultivating, 

 watering, and cleaning the plants. As a remedy they propose fur- 

 nishing the necessary conditions for vigorous, healthy plant growth 

 at all times. This is a good doctrine, but begs the question. 



FUNGOUS NATURE OF THE DISEASE. 



Over four years ago the writer succeeded in producing upon violet 

 leaves spots that were in every way identical with those above described 

 by spraying the leaves with distilled water to which spores of the fun- 

 gus Alternaria vioim had been added. Since that time he has proved 

 by nmuerous laboratory and greenhouse experiments (details of which 

 will appear in the following pages) that the so-called ''spot disease" 

 of the violet is unquestionably due to the attacks of this fungus. 

 Other fungi, Cercosjxjra viohe Sacc, F/iyUostictavwhv Besm.. Sepforia 

 violce Wesid., etc., are known to attack the violet, producing upon the 



