DISEASES OF CULTIVATED PLANTS 639 



ture and ammoniacal solution of copper carbonate, seem to show 

 that they possess little or no value in preventing the disease, while 

 on the other hand they render the foliage worthless for bunching 

 with the flowers, and thus occasion considerable loss and incon- 

 venience. From the writer's experience and that of many others 

 it would seem that the solution of this problem of controlling the 

 disease lies in preventing it by giving careful attention to the pro- 

 duction of vigorous, healthy, plant growth rather than in attempt- 

 ing to check the trouble after it has once gained a foothold. 



The successful growing of violets free from disease and the 

 production of flowers of the best quality are governed by a number 

 of factors which must be kept in mind. The principal rules which 

 should govern the grower are the following: 



(1) Study carefully the behavior of the plants under the vary- 

 ing conditions surrounding them. Endeavor by modifying these 

 conditions, when necessary, to secure plants of ideal development. 

 Set the standard of excellence high and be satisfied with nothing 

 short of its attainment. 



(2) Grow the plants during the entire season where they can 

 be given the conditions necessary for making a vigorous, healthy 

 growth, and where they can be protected at all times from condi- 

 tions likely to induce disease. 



(3) Keep the houses or frames clean, sweet, and in perfect 

 condition for growing healthy plants, by repairing and painting 

 them when necessary, and by removing and destroying all rubbish 

 likely to harbor vermin or disease. 



(4) Propagate only from healthy, vigorous stock of known 

 parentage at the season most favorable to the plants. 



(5) Select each spring none 'but perfectly healthy, vigorous 

 plants from the rooted cuttings for planting into the houses or 

 frames. Old plants are sometimes carried over, and occasionally 

 yield a large crop of flowers. They are not as reliable as the young 

 plants, however, and are much more liable to all kinds of disease. 

 The best growers rarely use them if it is possible to secure strong, 

 healthy young plants for spring or early summer planting. (Div. 

 Veg. Path, and Phys. B. 23.) 



(6) Keep the plants clean of yellow, dead, or dying leaves, 

 being careful to destroy them after removing them from the plants. 



(7) Keep the plants free from insects and other animal pests. 



(8) Give careful attention to ventilating, heating, and shad- 

 ing the houses or frames and to watering, cleaning, and cultivating 

 the plants. 



(9) Renew the soil in the beds each season before setting in 

 the young plants by removing from eight to twelve inches of the 

 surface soil and replacing it with that freshly prepared. 



(10) Set the young plants early in the spring in the beds where 

 they are to remain during the season, so that they may get well estab- 

 lished before the hot, dry weather of summer makes its appearanc. 



Careful attention given to the above directions for a number 

 of years will, it is believed, result in the production of a strain of 



