1910.] PUBLIC DOCUMENT — No. 31. 51 



Lettuce. 



Many years ago lettuce growers were troubled with a disease 

 known as top-burn, and amatenr growers have it to contend with 

 at the present time. The disease is characterized by the margins 

 of the young leaves becoming wilted and dying from a collapsing 

 of the tissue. The older and more skilled lettuce growers early 

 learned that the trouble was not associated with fungi, and it 

 could be easily controlled by the adjustment of the day and night 

 temperature to the conditions of the weather. It has been found 

 that if the night temperatures are kept too high, — 50° or more 

 in cloudy weather, — top-burn w^ill follow, if the following day 

 is clear and the day temperature reaches as high as 70° or 80°. 

 By carefully maintaining low night temperatures, 40° or 45°, 

 during cloudy periods, and holding the day temperature down, 

 top-burn can be prevented. On the other hand, in bright, sun- 

 shiny weather, higher day as well as night temperatures may 

 be maintained without running the risk of getting top-burn. 



Lettuce as well as other indoor crops must be grown according 

 to the weather, and as no two seasons are alike it follows that 

 no two crops can be grown precisely alike. Every successful 

 greenhouse grower realizes this and handles his crop accord- 

 ingly. 



CHRYSANTnEMUMS. 



The chrysanthemum is affected with three diseases, Avhich can 

 be controlled if attention is given to proper methods of culture. 



Leaf blight (Cylindrosporium), similar to that on the tomato, 

 occasionally affects more or less badly the lower leaves of chrys- 

 anthemum plants when grown to a single stem close together. 

 This leaf spot, like the one on tomatoes, is caused by too close 

 planting, which shuts out the light and prevents the circulation 

 of air. More open planting, or anything which would allow 

 more light or freer access of air, will prevent it. 



The chrysanthemum rust, which once caused considerable 

 alarm, can be prevented by paying attention to watering. Some 

 greenhouse growers are often troubled with this rust, while 

 others have never had the least indication of it. Even if two 

 growers buy their stock from the same concern, and it is identi- 



