MUTATIONS 277 
a species in which the transformation into new forms was proceeding 
on a scale large enough to make possible the direct observation of species 
formation. In none of the particular races that he collected did he 
observe profound discontinuous variations until in 1886 he discovered 
a feral group of large-flowered evening primroses (Q!nothera lamarckiana) 
growingin a suburb of Amsterdam. They had escaped into an abandoned 
potato field from a nearby park. The source of this particular even- 
ing primrose has been traced by de Vries. About the middle of the 19th 
Fia. 114.—Cénothera lamarckiana. (From a painting. See de Vries, Gruppenweise Art- 
bildung.) 
century seeds of i. lamarckiana were imported into England from Texas. 
De Vries’ race came from an estate near Hilversum, the seed having 
been obtained originally from an establishment in Erfurt, which de 
Vries thinks must have obtained their seed from England. It has never 
been found as an indigenous species either in Europe or America. This 
beautiful plant is much prized as an ornamental and is known to have 
escaped from cultivation in various places. 
“Tamarck’s evening primrose is a stately plant, with a stout stem, attaining 
often a height of 1.6 meters and more (see Fig. 114). When not crowded the 
main stem is surrounded by a large circle of smaller branches, growing upward 
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