INTUMESCENCES • 



143 



mg 



color of the leaves. Dandeno concluded from his research 

 that " the alkali kills the tissue in direct contact with the 

 irritant; it stimulates the abnormal development of the 

 tissue immediately around the spot." 



Aside from the stimulating activity noted above, there 

 have been frequent references to the stimulating effect of 

 various salts on both higher and lower plants. Small addi- 

 tions of zinc or magnesium have frequently been found to 

 increase the crop of spores in fungi 17, 21 . The results 

 of all of these investigations show that various dilute solu- 

 tions, generally of inorganic salts, may have a beneficial 

 effect upon growing cells up to a certain concentration. 

 This beneficial effect is evidenced in more vigorous assimi- 

 latory activity and increased production of chloroplasts, and 

 in some cases in an increased cell production. After reach- 



a certain concentration, the action of the salt has 

 usually been that of an irritant poison, which usually re- 

 sulted in the temporary disabling and generally in the death 

 of the cells affected. The only cases where the action of 

 a probable poison resulted in growth at all comparable to 

 the intumescences above described, is in connection with 

 various insect galls. It is probably true that the formation 

 of insect galls is due to some chemical influences exerted 

 either by the parent insect, the egg or the larvae, and as a 

 result of these influences, oedematous cells are sometimes 

 produced, as described by Kustermacher 13 , Kiister 10 , and 

 Woods 39 . 



i 



In none of the effects noticed as a result of the action of 

 chemicals on leaves, with the possible exception of insect 

 galls, has any change in the tissues, such as the oedemas 

 described, been noted. Where copper salts were absorbed 

 there was either a stimulus in the way of increasing pro- 

 duction of cell contents, or increased assimilation, or where 



solutions were used, the cells were destroyed 





stronger 



entirely. In the case* of the cauliflower intumescences, 

 there is a very evident stimulation resulting from the appli- 



