244 GOTE TURESSON 
hereditary branching types, one erect in ordinary light and one prost- 
rate in ordinary light (A. latifolium and A. patulum), of which the 
‚former type could be induced to become more or less plagiotropic when 
exposed to light of great intensity. An erect type of A. litorale was 
also experimented with on that occasion, but this was found to be 
the least sensitive of the different forms (belonging to other species) 
tried. Since then instances of modificatory prostrateness have also 
been found in A. li- 
torale. It is espe- 
cially the procum- 
bent biotypes which 
are apt to become 
modified in that 
way. Prostrate mo- 
difications almost 
always result when 
individuals belong- 
ing to these types 
are allowed to de- 
velop in the sand 
culture, where much light 
is reflected from the white 
sand and where the plants, 
because of their reduced 
size, do not shade one ano- 
ther. Fig. 17 shows the ha- 
bitus of two individuals be- 
longing to the same biotype 
Fig. 17. Atriplex litorale, field no. 159. The (list no. 159) of which the 
“Péanditions the lower plant raised in . UPP¢T. Plant has been raised 
an CULE in the ordinary field cul- 
ture, while the lower plant 
illustrates the modificatory prostrate habit of growth attained in the 
sand culture. When modificatory and hereditary prostrates occur 
_together on the exposed beach some difficulty is experienced in sepa- 
rating the different types, and the cultivating of the forms becomes 
necessary. Prostrate modifications of erect types have not been found. 
The ascending types may become influenced to a limited degree and 
are then hard to distinguish from the procumbent types. These latter 
are most readily induced to become prostrate. 
