300 Non-Isolable Races. 
capacity to do this is present in them in a semi-latent 
state. 1 
With Oenothera Lamarckiana I have made some more 
extensive experiments on accelerating the development of 
the stem by improving the conditions of growth. In the 
wild state this plant consists chiefly of biennials, but 
partly also of annual and of triennial individuals. Under 
experimental conditions, however, the duration of its 
life seems to depend more on external influences than 
on the choice of seeds. I have especially tested the 
distance between the plants, the sunniness of the position, 
and the richness of the soil. 
In 1888 I selected some seeds of my biennial stock 
plants of the Lamarckiana family of 1 886-1887, 2 in order 
to investigate the effect of the degree of separation of 
Jie plants in the bed. For this purpose I selected four 
adjacent beds of similar contents with regard to soil and 
manure, sowed the seeds in the middle of April fairly 
thickly in rows, and weeded them out during germina- 
tion in such a way that on two beds the plants stood at 
moderate distances, on one further apart, and on a 
third more closely. In the summer up to the middle of 
September I recorded the number of individuals with 
stems and the number of the rosettes. The sum of the 
two obviously affords a measure of the distances between 
the plants. The extent of each bed was 13 square meters. 
The figures are : 
* Sur la culture des monstruositcs, Comptes rendus de 1'Ac. d. 
Sc., Paris, January, 1899; Sur la culture des faseiations des especes 
arniuelles et bisannuelles, Revue generale de botanique, Vol. XI, 
1899, p. 136; and Ueber die Abhdngigkeit der Fasciation vom Alter 
bei sweij'dhrigen Pftanzen, Botanisches Centralblatt, Vol. LXXVII, 
1899. 
* See the pedigree in Vol. I, p. 224. 
