20 



growth, such as the use of highly nitrogenous soil or too much 

 water, is likely to cause hollow stem. He further found that 

 quickly growing varieties are more likely to be atfected, and that 

 transplanting before hardening off the plants is favorable to the 

 trouble. He advocates the use of less nitrogenous fertilizers, 

 less crowding in the seed-beds and such conditions as will give 

 rise to less rapid growth in the plants. 



OEDEMA 



This peculiar trouble of greenhouse tomatoes was first in- 

 vestigated by G. F. Atkinson^ of Cornell University, who made 

 an exhaustive study of it. He diagnoses the disease as follows : 



"Oedema of the tomato is a swelling of certain parts of the 

 plant brought about by an excess of water, which stretches the 

 cell walls, making them very thin and the cells very large. The 

 excess of water may be so great that the cell walls break down, 

 and that part of the plant dying, exerts an injurious influence in 

 adjacent parts." 



The cause of Oedema is insufficient light, too much water in 

 the soil/and too high a moisture content of the air. It is an 

 abnormal disease of very rare occurrence, and should cause no 

 trouble if good judgment is exercised in growing the plants. 



Oedema is easily produced by maintaining too moist an at- 

 mosphere and too high a soil temperature. 



MOSAIC DISEASE 



The so-called mosaic disease^, which is common to tomatoes, 

 is characterized by a peculiar yellow spotting of the upper surface 

 of the leaves. These yellow spots, particularly when exposed 

 to bright sunlight, subsequently become purplish in color, and the 

 margins of the leaves curl up. We have observed many crops 

 badly affected w-ith what is termed "mosaic trouble," and in all 

 cases this is associated with too extensive pruning. The more a 

 tomato plant is pruned the more likely it is to be affected with 

 the mosaic disease, and topping or pruning of the leaders induces 

 this trouble more than other* methods of pruning. 



The mosaic disease is apparently a functional trouble, and 

 little is known about it. Similar troubles are associated with 

 tobacco (calico) and are believed to be infectious. The presence 

 of this disease on tobacco is thought by some to be associated 



1. X. Y. (Cornell Univ.) Agr. Exp. Sta., Bui. No. 53, 1893. 



2. Bur. Plant Ind., U. S. Dept. Agr., A. F. Woods, Bvil. No. 18. 



