189 ^] NATURAL SCIENCES OF PHILADELPHIA. 85 



I will give a strikiug illustration of the soimduess of this principle, 

 which I have not hitherto recorded, in Corylus ro.itrata. 



In one of my earlier papers^ I recorded that there was a uni- 

 form line of character dividing the species of western Europe from 

 their close allies in eastern America. Among other points, the 

 tendency to lateral branching is more marked in the European 

 than in the American line of the same family. Corylus Avellanct, 

 and Corylus rostrata, which I had not in that list, are good illus- 

 trations. In a cubic yard of growth there would seem to be hun- 

 dreds of twiggy branchlets in Corylm Avellana, the common Euro- 

 pean Hazelnut, to the scores only in the North American Hazelnut, 

 Corylus rostrata. It is important to note this difference in these 

 species, in connection with these sexual questions, because at first 

 glance the male catkins seem terminal in the European, and axillary 

 in the American. The male catkins seem situated on comparatively 

 strong branchlets ; while the female buds seem to be on branchlets 

 often weaker, and situated below the males and more unfavoi'ably 

 located as regards nutrition. That this is deceptive will hereafter 

 be showfl. 



The branching of Corylus rostrata is remarkable for its stiff rigid 

 character. It might be taken for some willow at first sight, rather 

 than a relative of Corylus Avellana ; although this latter species has 

 this culm-like or reedy appearance before the plant reaches its flow- 

 ering stage. The flowers appear along the Avhole length of these 

 rigid branchless stems. The male flowers are produced from the 

 lower nodes, and the female from the upper ones. But the j^ropor- 

 tion of each on the separate branches is in exact j^Toportion to the 

 vigor of the branches. On a very slender twig of perhaps twelve 

 or fifteen nodes, there will be a male catkin from every bud. On 

 the branches of medium strength the proportion of male to female 

 will be equal, while on the branches of superior vigor all but three 

 or four of the lower ones will be female. On a strong leading 

 shoot before me, and which is charactei'istic of numbers of others 

 on the plant from which it was taken, the four lower buds only 

 have catkins; while the ten upper buds have either female flowers 

 or a few strong buds to make branchlets for next season. 



No one closely observing a vigorous plant of Corylus rostrata can 



^ " On the Eelative Characters of Allied Species of European and Americau 

 Trees" (Proc. Acad. Nat. Sci. Phila., 1862, p. 10). 



