59 



"The introductory part of this report dealt with the various cases of 

 artificial and natural wounds in higher plants and with the description of con- 

 trasted types of wound healing and structural regeneration in organs and 

 tissues of different structure and reactivity. The stages in the readaptation 

 process of cells in wound tissues : dedifferentiation, cell growth and division 

 and redifferentiation were described. The histological and metabolic changes 

 during wound meristem activity and the effects of external and internal 

 factors on cell division and differentiation, such as polarity, light, temperature, 

 oxygen, water, pH, food distribution, enzymes and growth substances were 

 discussed. The effects of necrotic and necrobiotic changes in the wound area 

 on processes of cell division, and of normal or pathological dedifferentiation 

 in adjacent cells were discussed in conjunction with the hormone hypothesis. 

 A brief history of the concept of the wound hormone and its experimental 

 isolation was given. 



In many cases tissues comparable to wound tissues can be produced by 

 an extreme change in external conditions, for example by high humidity 

 (hyperhydric tissues, such as lenticel proliferations and intumescences), by 

 darkening parts of the shoot, and by chemical stimulation (e.g. callus and 

 adventitious root formation). 



Wounding, therefore, may be regarded as one way of disturbing the 

 normal physiological continuity of a plant and setting into motion a regulating 

 reaction mechanism, of which, for example, structural regeneration is one 

 visible expression. The question as to the exact interaction and nature of the 

 factors concerned in this control must at present remain unanswered, but for 

 the process of restoration of anatomical features at and near the surface of 

 wounded organs a casual explanation seems available. Certain layers of cells 

 below the wounded surface become meristematic, and this portion of the 

 organ resumes development in so far as thickening of cell walls and con- 

 densation and oxidation processes near the surface produce histological and 

 chemical characters similar to those developing during normal differentiation 

 of the organ. 



A brief discussion of the characteristics of plant-neoplasms, chemical and 

 bacterial tumors, so-called spontaneous tumors of hybrids, and of insect galls 

 concluded the lecture." 



Clyde Chandler 

 Recording Secretary 



Meeting of December 5, 1939 



The meeting of the Torrey Botanical Club, held at the American 

 IMuseum of Natural History on December 5 was called to order by 

 the President at 8.15 p.m. 



Fifty-seven members and friends were present. 



The following were elected to annual membership : Dr. A. R. 

 Bechtel, Wabash College, Crawfordsville, Ind. ; Dr. J. F. Brenckle, 



