THE GENOTYPICAL RESPONSE OF THE PLANT 225 
where species of the inland swamp (Ranunculus flammula, Lycopus, 
Scutellaria, Caltha, Comarum etc.) occur mixed with typical salt mea- 
dow plants (Plantago maritimum, Glaux, Armeria). The point in 
question will be discussed more fully in a following chapter. 
Fig. 5 illustrates some of the different types now seen in the cul- 
tivated series no. 35. It should not be thought, however, that varia- 
tion does not occur with regard to other characteristics: Differences 
between the plants are also seen in the matter of the hairiness of the 
leaves, in the shape of the leaf margin, in the shading of the blue 
flower colour, etc. These characteristics have been found to repeat 
themselves, in those plants observed, every year, and thus strengthen 
the belief-in the hereditary nature of the characteristics in question. 
In summarizing the results of the cultivations the following con- 
clusions seem most reasonable. The hereditary variation in height be- 
comes covered by the modificatory dwarfing cf the plants when ex- 
posed to the more or less extreme conditions in the natural salt mea- 
dow habitat, resulting in a seemingly homogeneous population of 
dwarfs known under the name f. nana. When brought into culture, 
the population breaks up into its component parts, and the great 
hereditary variation as to height becomes visible. The fact that in- 
dividuals, found upon culturing to be constitutionally as tall as those 
of the inland swamp population, are found to be contained in certain 
dwarf populations, while they are excluded from others, points to the 
controlling effect of the habitat factors upon the hereditary composi- 
tion of the population. | 
C. CENTAUREA JACEA. 
This species is also found growing in the salt meadows along the 
coast in a much dwarfed form, f. humilis Schrank., about 10 cm. high, 
or even less. Fig. 6 illustrates the general appearance of this dwarf 
as it is found growing at Vellinge. One of these Vellinge dwarfs was 
brought into culture as long ago as 1916. It increased in height the 
following year, and then measured about 35 cm. In 1918 it attained 
a height of about 50 cm., and has since kept this height, with slight 
fluctuations in response to the yearly fluctuations of weather condi- 
tions. The plant was divided in 1920, and fig. 7 represents an indi- 
vidual of the resulting clone. A dwarf transplanted in 1917 from 
Torekov behaved in a different way. It should be said that f. humilis 
grows abundantly at this place together with the dwarf Succisa dealt 
