96 Sudden Appearance and Constancy. 
In contradistinction to these more or less distributed 
varieties, there is a whole series of records scattered 
through the literature of cases in which a new form has 
been found on a particular spot under circumstances 
which warrant the conclusion that it has arisen exactly 
there and fairly recently. In such cases transitional forms 
are always lacking, a fact which proves pretty conclu- 
sively that such have not been produced in the origination 
of the form. In Part II of the first volume two cases 
afforded by Oenothcra Lamarckiana were described in 
detail : I refer to the appearance of O. brevistylis and O. 
lacvi folia on the original locality at Hilversum. Both 
species proved, when tested, to be perfectly constant from 
seed, without any atavism; and transitional forms were 
not seen in the field. If these species had arisen where 
I found them, their origin must have taken place between 
the year of the introduction of the species and the first 
year in which I discovered them; that is, between 1870 
and 1886 (See Vol. I, p. 266). 
The most important and accurate observation of such 
an occurrence is that which has recently been recorded 
by SOLMS-LAUBACH, and deals with a species newly 
arisen from Capsella Bursa Pasioris. 1 This was found 
by Professor HEEGER in the market place near Landau 
amongst the ordinary Shepherd's purse and called C. 
Hccgcri after him, by SOLMS. It occurred in 1897 and 
1898 in very small numbers and only on this one spot. 
In its vegetative parts it is exactly like C. Bursa pastoris, 
from which it only differs in the form of its fruits. But 
the differentiating characters are of the rank of some of 
1 H. GRAF zu SOLMS-LAUBACH, Crucifcrcn-Stiidicn, Botanische 
Zeitung, 1900, Heft X, Oct., i, 1900, pp. 167-190, Plate VIII. 
