12 



atmosphere is dry. but it is also active even where there is more 

 or less moisture when the sun is bright. 



The influence of sunlight on the blossom end rot is very 

 clearly shown in the susceptibility of crops grown at diiTerent 

 seasons. In the fall, when the light is poor, the disease is un- 

 common in the greenhouse, whereas as the season advances and 

 the sunlight becomes more intense, the blossom end rot increases. 

 In a greenhouse the sunlight from February on is comparatively 

 intense, and it is then that the blossom end rot is most trouble- 

 some. It is also more common in a house where the atmospheric 

 moisture is kept down. The plants in our experiments were in 

 all cases grown in benches more or less close to the glass, with 

 the rows not very close together, which is not often the case in 

 commercial houses. When tomatoes are planted so closely that 

 they are more or less shaded, the light is not such an important 

 factor in causing rot. The proximity of tomatoes to steam and 

 hot-water pipes is conducive to rot, since the heat accelerates 

 transpiration ; moreover, the soil dries out more quickly under 

 these conditions and root absorption is decreased. In practically 

 all of our experiments those plants located near steam pipes and 

 at the ends of beds were more susceptible to rot than others. In 

 the spring, when the sun is very bright, partial shading of the 

 plants by whitewashing the glass or other means should prove 

 useful in holding the rot in check by lessening transpiration. 



Fertilizers and manures are also capable of inducing a tend- 

 ency to rot, since they modify root absorption more or less and 

 restrict the amount of water which the plant can take in. The 

 greatest source of danger in this respect occurs in the excessive 

 use of nitrates, and one should be careful in applying fertilizers 

 and manures containing large amounts of nitrates. Where there 

 is an excess of nitrates in the soil it can be easily detected by 



chemical analysis of the leaves. 



\ 



CONCLUSIONS REGARDING THE BLOSSOM END 



ROT 



From what has been stated regarding the various factors 

 which may influence blossom end rot it is quite evident that we 

 have here a complicated problem to deal with. Besides the 

 necessity of applying water freely to the roots as a means of 

 preventing the rot, it is well to pay attention to other factors, 

 such as light, heat, moisture, etc., which induce the rot if not 

 properly handled. 



In general, it may be said that sunshine is the principal de- 

 terminative factor in greenhouse management, since crops grow 

 and develop in proportion to the light they receive. It also afifects 



