98 Sudilcji Appearance and Constancy. 



to isolate it, and has maintained itself up to the present 

 day without ever reverting. 



So far as puhlished data go, forms which have sud- 

 denly appeared in nature, or have not previously heen 

 noticed, prove constant, provided that cross-pollination 

 is guarded against. In the opposite case they will prove 

 themselves pure as soon as they can be isolated. One 

 of the oldest cases in point is the constancy of Ranun- 

 culus arvensis inennis whicli was established by Hoff- 

 mann.^ The majority of records refer to trees of which 

 the larger number of varieties, if not all, according to 

 Darwin himself, have arisen suddenly,^ such as the 

 \veeping oak, the weeping white hawthorn, etc'^ A single 

 specimen"* of Fagus sylvatica aspleniifolia was found in a 

 wood in Lippe-Detmold and could be multiplied from 

 seed. According to Loudon, Taxus haccata fasfigiafa 

 was found in 1780 growing wild in Ireland ;'^ but no pure 

 seedlings of it have been obtained since only one speci- 

 men w^as observed (a female one). 



The above list of cases is not a rich one ; but it makes 

 no claim to completeness. The observations in point are, 

 with few exceptions, relatively incomplete inasmuch as 

 there is always the possibility that the first discovery of 

 the new species or variety may have been preceded by 

 a long period of evolution. If we assume this to be true, 

 the absence of transitional forms and th^ constancy of the 



^ Hoffmann, Bof. Zcitung, 1878, p. 273, where several other 

 examples will be found. 



^Darwin, Variations, I, pp. 461-463. 



' Further examples are given by Braun, Vcrjiingiing, p. 333 

 (the sudden origin of red-leaved varieties of Quercus, CoryluSj etc.). 



* Ratzeburg, cited by Braun in Abh. d. k. Akad. Berlin, 1859, 

 p. 217. 



°L. Beissner, Handbuch dcr Nadclhohkundc, 1891, p. 169. A 

 great number of further examples is given in this work. 



