Taxonomic Anomalies 667 



seem to be also more inconstant when propa- 

 gated sexually. The difference is so striking 

 and affords such a reliable feature that Koch 

 proposed to make two distinct varieties of them, 

 calling the pure type Fraxinus excelsior mono- 

 phylla, and the varying trees F. exheterophyl- 

 la. Some writers, and among them Willdenow, 

 have preferred to separate the " one-leaved " 

 forms from the species, and to call them Fraxi- 

 nus simplici folia. 



According to Smith and to Loudon, the * ' one- 

 leaved " ashes are found wild in different dis- 

 tricts in England. Intermediate forms have not 

 been recorded from these localities. The same 

 mode of origin is that already detailed for the 

 laciniate varieties of alders and so many other 

 trees. Hence it may be assumed that the " one- 

 leaved " ashes have sprung suddenly but fre- 

 quently from the original pinnate species. The 

 pure type of Willdenow should, in this case, 

 be considered as due to a slightly different 

 mutation, perhaps as a pure retrograde variety, 

 while the varying strains may only be ever- 

 sporting forms. This would likewise explain 

 part of their observed inconstancy. 



In this respect the historic dates, as collected 

 by Korshinsky, are not very convincing. Vi- 

 cinism has of course, almost never been exclud- 

 ed, and part of the multiformity of the offspring 



