98 Sudden Appearance and Constancy. 
to isolate it, and has maintained itself up to the present 
day without ever reverting. 
So far as published data go, forms which have sud- 
denly appeared in nature, or have not previously been 
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 art'cnsis incnnis which was established by HOFF- 
MANN. 1 The majority of records refer to trees of which 
the larger number of varieties, if not all, according to 
DARWIN himself, have arisen suddenly, 2 such as the 
weeping oak, the weeping white hawthorn, etc. 3 A single 
specimen 4 of Fagns sylvatica aspleniifolia was found in a 
wood in Lippe-Detmolcl and could be multiplied from 
seed. According to LOUDON, Ta.rus baccata fastigiata 
was found in 1780 growing wild in Ireland; 5 but no pure 
seedlings of it have been obtained since only one speci- 
men was 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 the constancy of the 
1 HOFFMANN, Bot. Zeitung, 1878, p. 273, where several other 
examples will be found. 
2 DARWIN, Variations, I, pp. 461-463. 
3 Further examples are given by BRAUN, Vcrjungung, p. 333 
(the sudden origin of red-leaved varieties of Quercus, Corylus, etc.). 
4 RATZEBURG, cited by BRAUN in Abh. d. k. Akad. Berlin, 1859, 
p. 217. 
5 L. BEISSNER, Handbuch der Nadclhohkundc, 1891, p. 169. A 
great number of further examples is given in this work. 
