SEXUALITY AND THE ENVIRONMENT. 235 



therefore, we have instances of the plants flowering and 

 bearing male organs only before the highest effort of vital 

 energy is displayed — the preliminary and feebler effort being 

 capable of developing the andrcecinm alone. 



With regard to diclinous trees, many examples could be 

 found to illustrate the principle that the female flowers are 

 normally produced by stronger shoots than -the male. Mr. 

 Meehan has particularly called attention to this fact. For 

 instance, " Juglans nigra* exhibits three grades of growing 

 buds. The largest make the most vigorous shoots. These 

 seem to be wholly devoted to the increase of the woody 

 system of the tree. Lower down, the strong last year's 

 shoots arise from buds not quite so large. These make 

 shoots less vigorous than the other class, and bear the female 

 flowers on their apices. Below these are numerous small 

 weak buds, which either do not push into grow^th at all, or 

 when they do, bear simply the male catkins." 



Again, Castanea Americana bears two crops of male flowers, 

 the first of which disarticulate and are useless ; the second 

 appear about ten days later, accompanied by clusters of 

 females. Occasionall}' a tree will be entirely female. 



Mr. Meehan also calls attention to the fact that isolated 

 trees of Birch, though producing an abundance of male and 

 female flowers, very often have not a perfect seed. Hazels 

 are sometimes protogynous, sometimes protandrous ; and if 

 the latter condition prevail, there may be little or no fruit, 

 as often occurs in Pennsylvania. After making analogous 

 observations on American Maples, he summarizes his remarks 

 on the latter as follows : — 



" Male flowers do not appear on a female Maple-tree till 

 some of its vital power has been exhausted. 



* Laws of Sex in J. Nigra, Proc. Acad. N. Sci. of Phil., 1873, 

 p. 290. 



