70 



ROYAL HORTICULTURAL SOCIETY. 



Wimm., independent of the imperfection of the pollen, exhibits 

 no symptoms of weakness in its ontward appearance. The pos- 

 sibility must therefore be allowed that the vegetative growth of 

 other seemingly strong hybrids (as, for example, by far the greater 

 number of hybrid willows) is essentially weak, so as to prevent 

 them in the Darwinian struggle for life from competing with 

 their parent species. 



If all these circumstances are combined with the imperfection 

 of the pollen and the partial sterility of the ovaries, the com- 

 parative defect of vital energy in hybrids may be considered as 

 proved. Nor does the luxuriant growth of some contradict this, 

 as we know that it often accompanies suppressed fertility. Kcel- 

 reuter's views seem then to be confirmed, that the luxuriance of 

 hybrids arises from sterility. The most fruitful hybrids are 

 always less so than their parents. The weakness of the genera- 

 tive organs in very luxuriant hybrids induces an increase of 

 vegetative growth, while this is not the case in others which are 

 too weak to exercise such a reaction. 



The relation of the sexes is modified in hybrids. The propor- 

 tion between the male and female plants is different from what 

 it is in pure species. This indeed requires further proof, the 

 confined limits of his garden not allowing the author to make 

 as many experiments as he otherwise would have done with pure 

 species. His observations were therefore confined to the propor- 

 tions which exist respecting hybrid willows in free nature, where 

 the difference in the proportion of the sexes in hybrid and pure 

 species is very striking. Pure species, however, are not quite 

 equal in the number of their male and female plants. S.fra- 

 gilis, alba, pentandra, and triandra, which are so strikingly distin- 

 guished from other European willows by the double nectary of 

 their male blossoms, bear, at least in the neighbourhood of Breslau, 

 a greater number by far of male individuals than the species with 

 a single nectary, as S. cinerea, viminalis, purpurea, repens, &c. In 

 the former the males are more numerous than the females, in the 

 latter this is not the case. Males and females are in nearly equal 

 proportions in these, though with a slight preponderance of females, 

 while in the other the females are far more numerous. In arti- 

 ficial hybrids with one nectary, there are about ten females to one 

 male ; but when more than two species are combined, it should 

 seem that there are great differences ; but observations are at 

 present not sufficiently numerous to establish any decided law. 

 Wichura considers his observations on this matter to be quite 



