96 Siiihloi 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 lias 

 ])een found on a particular spot under circumstances 

 wliich warrant tlie conclusion that it has arisen exactly 

 there and fairly recently. In such cases transitional forms 

 are always lacking, a fact which proves pretty conclu- 

 siv^ely that such have not been produced in the origination 

 of the form. In Part II of the first volume two cases 

 afforded by Oenothera Laniarckiana were described in 

 detail : I refer to the appearance of O. brcvistylis and O. 

 lacvifolia 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 Capsclla Bnrsa Pastoris} This was found 

 by Professor Heeger in the market ]:)lace near Landau 

 amongst the ordinary Sh.epherd'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 



^ H. Graf zu Solms-Laubach, Crucifcrcn-Studicn, Botanische 

 Zcitung, 1900, Heft X, Oct., i, 1900, pp. 167-190, Plate VTTI. 



