406 De Vries . — On Biastrepsis in its 
February, no trace of spiral arrangement could be detected. 
A control-experiment, with sixty-two plants from the same 
seed, but planted twelve to the square metre, gave io per cent, 
of individuals with twisted stems. 
Hence lack of sufficient space can entirely prevent biastrepsis 
from making its appearance. 
A similar result was obtained with regard to the exposure 
of the beds. Shade, whether of trees or other objects, is 
always prejudicial ; a good proportion of twisted stems can 
only be obtained when the plants are grown in an open situa- 
tion fully exposed to the sun. Thus, in 1890, a sowing in the 
shade of a tree gave only 3 per cent., whilst another quite 
similar sowing, but with full exposure to the sun, gave 7 per 
cent, of plants with spiral phyllotaxis. 
The time for sowing the seed, whether in the open or in 
pans in the greenhouse, varies from March to the beginning 
of May. The time and mode of sowing seems to be of little 
or no importance as compared with the requirement of suf- 
ficient space. 
When sowing in the open, about 3-5 c.cm. of seed per 
square metre should be used, containing 200-300 seeds. Of 
these only a portion will germinate, and of these some are 
lost or are weeded out, so that eventually only about 20-25 
plants result. On the other hand, seeds sown in pans kept in 
the greenhouse nearly all germinate ; the seedlings are very 
uniform, and can be potted off without any selection. The 
latter method therefore yields by far the more reliable figures 
of the two. 
In weeding out the seedlings obtained by sowing in the 
open, either the most vigorous plants may be left, or no 
attention may be paid to this point ; but the result is 
materially influenced by the course pursued, for the weaker 
plants are much less likely than the vigorous to show 
twisting. They are plants which apparently have been badly 
nourished, either in the seed-stage whilst still on the parent, 
or during or after germination. I made an experiment on 
this point in 1888-9. In June, 1888, I planted two similar 
