268 rRocEi:D[N(is of the academy of [18!>0. 



tion furnishes the clue to the huv governing that abortion in flowers 

 which renders the hermaphrodite unisexual. In the maple, as in 

 the case referred to, there is a rest when the anther and pistil reach 

 a certain point. When growth is again resumed, the filament is 

 produced and the stamen elongates, while the pistil remains dor- 

 mant. Then we have fully developed male flowers. In another 

 case growth is resumed only by the gynwcium, the fully formed 

 anthers remaining sessile and barren at the base. Then we have the 

 female flowers in the maple tree. This arrest and resumption of 

 growth in the parts of flowers was noted by the author many years 

 ago in the flowers of the Compass Plant, Silphimn lacinlatum} 



The facts here noted in connection with the willow refer to the 

 male aments. 

 Ox THE Varying Character of Dichogamy' in Flowers 



OF CORY'LUS AveLLANA. 



In several papers, in recent years, I have noted that dichogamy is 

 not a fixed character in plants, Imnight about by any relation between 

 insects and flowers, but is aflected by climate and season. A species 

 proterandrous under one set of circumstances, will be proterogynous 

 under another. I have also shown that certain conditions of tem- 

 ])erature will aftect the female flowers or female organs of hermaph- 

 rodite flowers when the male organs will remain quiescent, and that 

 other conditions will advance the male organs rapidly, while the 

 female organs remain at rest. 



My observations on the hazel nut, (Jorylus Avellana, for several 

 years past have shown remarkable variations. A few very warm 

 days in cold winters will bring the male flowers to perfection two 

 months before the female flowers open, dying away so completely as 

 not to leave any for fertilization, so that the plants would be wholly 

 barren for that season. Occasionally the openings of the male and 

 female flowers have been nearly simultaneous, when a good crop of 

 nuts from complete fertilization has resulted. 



This season is the first since the observations have been under- 

 taken when the results have been reversed. The female flowers are 

 now (Jan. 11th, 1890) abundantly in bloom, while the catkins are 

 far from mature. In former years the flowers have always been 

 proterandrous — this season they are proterogynous. 



Although the deductions I have heretofore made — that male 

 flowers, or male organs of flowers, mature rapidly under a com- 



1 Ibid, 1870, p. 117. 



