1883.] NATURAL SCIENCES OF PHILADELPHIA. 85 



base of the flower, as in that figure, warranting the var. Wrightii 

 Eng. 



On the Relations of Heat to the Sexes of Floioers. — At the 

 meeting of the Botanical Section on April 9, Mr. Thomas Meehan 

 referred to his past communications to the Academy, showing that 

 in monoecious plants female flowers would remain at rest under 

 a temperature which was sufficient to excite the male flowers to 

 active development. Hence a few comparatively warm days in 

 winter or early spring would bring the male flowers to maturity, 

 while the female flowers remained to advance only under a higher 

 and more constant temperature. In this manner the explanation 

 was offered why such trees were often barren. The male flowers 

 disappeared before the females opened, and hence the latter were 

 unfertilized. He referred especially to some branches of Corylus 

 Avellana, the English hazel-nut, which he exhibited before the 

 Section last spring, in which the male flowers (catkins) were past 

 maturity, the anthers having opened and discharged their pollen, 

 and the catkins crumbling under a light touch, but there were no 

 appearances of action in the female flower-buds. There were no 

 nuts on this tree last season. The jiresent season was one of un- 

 usually low temperatui'e. There had not been spasmodic warmth 

 enough to bring forward the particularly^ excitable maple-tree 

 blossoms. The hazel-nut had not, therefore, had its male blos- 

 soms brought prematurely forward. He exhibited specimens 

 from the same tree as last season, showing the catkins in a young 

 condition of development, only half the flowers showing their 

 anthers, while the female flower-buds had their pretty purple 

 stigmas protruding from nearly all of them. 



Mr. Meehan remarked that his observatiqiis the past few seasons 

 had been so carefully made that he hardly regarded confirmation 

 necessarjr, but believed the further exhibition of these specimens 

 might at least serve to draw renewed attention to his former com- 

 munications. 



April 11. 

 Rev. Henry C. McCook, D. D., Vice-President, in the chair. 

 Twenty-two persons present. 

 The following was ordered to be printed : — 



