122 Agricultural Experiment Station, Ithaca, N". Y. 



also acquired their characteristic features. In the No. 18 plant, figure 

 17, at the same stage of growth there are as yet no cells presenting the 

 characteristics of woody or bast cells. The presence of the woody 

 cells themselves probably does not exert any influence in checking the 

 tendency on the part of the cells of the fundamental tissue to stretch 

 under the influence of turgescence. But it indicates a slower rate of 

 tissue growth and firmer and, therefore, more resistant cell walls in the 

 fundamental tissue. 



There is, perhaps, some inherited disposition on the part of different 

 varieties to this trouble. The history of the No. 18 strengthens this 

 view. The original plant was remarkable for its rank growth, abun- 

 dant foliage and wide reach of limb, so that it was trained to lateral 

 supports similar to some methods of grape training. 



But there are also individual variations in the firmness or succulent 

 pulpy nature of the stems, dependent upon varying conditions of 

 growth and environment. This is a matter of common observation in 

 all plants. The individual variations in the succulency or firmness of 

 the tissues of the tomato plant render them mo.re or less susceptible to 

 the trouble. 



Relation of growth to the develo2Wient of the cushions. The rela- 

 tion of the actively growing parts of the plant to these (Edematous por- 

 tions also lends support to the view that they are the result of excessive 

 turgescence. Turgescence is one of the first conditions of growth, and 

 other things beiug equal, rapidity of growth and the proportions of the 

 growing shoot bear a close relationship to the degree of turgescence. 

 The greater the degree of turgescence the larger will be the cells and 

 the thinner their walls. Where the growing shoot or leaf meets with 

 no obstruction to growth, the multiplication of cells and their enlarge- 

 ment and disposition into the various tissue elements accommodates all 

 the water which by root pressure is distributed to them. The rate of 

 growth is sufticient to relieve the great pressure though transpiration 

 may be below the normal rate. Transpiration takes place more 

 rapidly in young leaves* and shoots, but I do not think the difference 

 in the susceptibility of very young and somewhat older tissues bears 

 any very great relation to their different capacities for transpiration as 

 will be shown below. 



In the plants which have been most susceptible to the trouble, it has 

 been very noticeable that the growing shoot for four to six inches was 

 entirely free from the cushions, while below this rapidly growing 

 region the turgescence effected the abnormal stretching of groups of 

 cells. The rate of growth at this point having declined, the excessive 



* Sachis' Physiology of plants. 



