PROCEEDINGS OF THE CLUB 15 



One frequent pattern in plants, which forms a common feature of generally more 

 complex tissue patterns, is formed by successive layers of suberized cells, lignified, sclerotic 

 elements and parenchymatous cells, arranged in concentric fashion. This pattern is often 

 developed as a dermal pattern, adjacent to a great variety of external and internal, normal 

 and pathological surfaces, cellular centers, and lacunae (e.g., hypodermis, exodermis, sec- 

 retory ducts, necrotic centers) . In Monstera deliciosa, this pattern could be induced or re- 

 generated in various positions, but always in conjunction with an outer or inner surface. 

 The developmental potency of forming this pattern is not reached before the cells and 

 tissues have attained a certain age, but is still present in comparatively old, differentiated 

 parenchyma and collenchyma cells. External conditions, such as oxygen supply and hu- 

 midity, influence the character of the pattern; and intracellular changes also suggest that 

 metabolic processes, at or near surfaces, are instrumental in the induction of this pattern. 



Another example of regeneration of histological pattern is the differentiation of xyleih 

 strands in vacuolate parenchyma cells in the wounded internode of Coleus. The plane of 

 cell division and wall differentiation do not show here as immediate a relation to the 

 wound surface as in Monstera. However, the bands of lignified thickening in successive 

 groups of differentiating xylem cells show an orderly arrangement, both in relation to 

 each other and to a visible configuration in the cytoplasm (granules and streaming) which 

 precedes them. This suggests the presence of a cytoplasmic pattern which, corresponding 

 to the phragmosome in cell division, is here the basis of differentiation in the cell wall. 



In both Coleus and Taraxacum older xylem elements are gradually dissolved in the 

 wound tissue; this process is initiated by the formation of tyloses in the vessels. 



The formal meeting adjourned at 4:40 p.m., but an informal discussion 

 of Dr. Bloch's paper continued over the refreshments generously provided by 

 the ladies of The New York Botanical Garden. 



Respectfully submitted, 



Edwin B. Matzke 

 Corresponding Secretary 



Minutes of the Meeting of February 1, 1944 



The meeting was called to order at 8 :20 p.m. by President Levine in Scher- 

 merhorn Hall, Columbia University. Forty-four members and friends were 

 present. 



The minutes of the preceding meeting were approved as read. 



Twelve persons were unanimously elected to annual membership, and two 

 to associate membership. One transfer from associate to annual membership 

 was approved. Dr. Roland Harper was unanimously elected to honorary life 

 membership. The resignations of 25 annual members and of 31 associate mem- 

 bers were accepted with regret. 



