306 Cook : Hypertrophied fruit of Bucida 



substance, a part of which was tannin. Near the tip of the pod 

 the cells were clear and evidently in a very active growing condi- 



tion. The intermediate cells showed every stage between those 

 of the two ends. 



The mites were scattered throughout but were much more 

 abundant near the tip than in any other part. Furthermore, many 

 of those near the tip were smaller than those near the base. 



Several species of mites produce hypertrophied conditions in 

 plants grading from a simple erinium to well-defined galls. The 

 simplest erinium may consist of unicellular outgrowths from the 

 epidermis while the more complex forms develop masses of multi- 

 cellular trichomes which are frequently accompanied with swellings 

 of the parts from which they arise. In some instances the normal 

 organs of the plant (usually the leaves of floral organs) become 

 very much convoluted, while in other cases there is a swelling in 

 which there is a well-defined cavity containing the mites. In most 

 cases there are numerous papilla-like growths of the parenchyma 

 projecting into these cavities. 



When these hypertrophies reach a maximum growth, there is 

 always a deposit of tannin. At this time the mites migrate towards 

 the tip and attack the young and more actively growing parts. 



From this discussion it will be readily seen that the ana- 

 tomical character of these abnormal fruits corresponds with those 

 of the well-defined Eriophyes galls. 



Agricultural Experiment Station, 

 Newark, Delaware. 



