THE GENOTYPICAL RESPONSE OF THE PLANT 219 
ordinary type in having culms taller and slacker and loosely tufted, 
long, drooping and dark or light green leaves, slack, long and somewhat 
drooping, never violet-coloured, panicles, smaller spikelets, and smooth 
flowering scales. Sets of this form have been collected and transplan- 
ted from Denmark (near Copenhagen) in 1919 (17 individuals), and 
from Dalby in Scania in 1921 (16 individuals). The changes brought 
about in the cultivated shade form as compared with the plants in 
their natural habitat are the following. The culms become more 
tufted, although the tuftiness of the main type is not attained. Both 
leaves and the panicles become brightly violet-coloured, and more so 
than is generally seen in the main type. The thickness of the leaves 
increases. The mean thickness of the basal leaves of two individuals 
from the Dalby series was found to be 135—155 mw. and 140—150 u. 
in their natural habitat in 1921, while the mean leaf thickness of the 
same plants the following year (1922) in culture was found to be 
150—175 x. in the one plant and 165—185 4. in the other. Whether 
the leaf thickness of the main type, the leaves of which are conside- 
rably thicker, has been attained in any of the plants of the Copenhagen 
series, which has been in culture since 1919, has not been ascertained 
with exactness, but to judge from superficial examination this is not 
yet the case. 
The length of the culms as well as of the leaves has been found 
to increase in the cultures. The mean leaf length, for instance, in the 
Dalby series (measuring 10 of the longest basal leaves of each plant) was 
found to be 425 mm. in 1921, while it was 530 mm. in 1922. An 
increase in the length of the panicles has also been found to take 
place in culture. 
The above results favour the assumption that D. glomerata var. 
lobata is a hereditary shade variety and not a modification due to the 
direct effect of the environment. Although undoubtedly certain charac- 
teristics ascribed to the form are the results of the extreme environment, 
as for instance the great looseness of the tuft and the pure green colour 
of the leaves and panicles, which characteristics disappear in culture, 
other characteristics, as the length of the leaves, culms and panicles, 
increase in magnitude upon cultivation. This would not be likely 
to take place had the plant in question developed its characteristics 
in direct response to subdued light. 
The variation within the series is otherwise rather large. Fig. 2 
represents the shape of the panicle in fruit from 4 individuals of the 
Copenhagen series. The same relation as to the degree of spreading 
