42 TYPES OF BRITISH PLANTS 
Here the seed is provided with teeth, which are all set 
at a particular angle. This angle prevents the fruit from 
moving except in one particular direction, but the part 
which has no teeth is very subject to the influence of 
damp. It alters its shape according to the amount of 
moisture in the air, and as it changes shifts the seed 
from side to side. The teeth ensure that the plant shall 
only move in one direction, and so it slowly travels 
forward. 
Some plants depend upon rain for the dispersal of their 
families, and the “Rose of Jericho,” which was very 
famous in the time of the Crusades, has an elaborate 
arrangement with a view to this. When the seeds are 
ready to go, if the weather remains dry, all the branches 
of the plant curl over the seed-vessel, and wait there till 
the rains begins. Then they open, for the seeds have 
now a chance of being nicely planted by the rain. The 
showers come on, the seeds are washed out and carried 
along to some convenient crack. The sea sometimes 
performs a similar office, but there are no land-plants 
which seem specially to lay themselves out for its opera- 
tions. Still, floating seeds like the cocoanut have been 
known to spread in this way from one South Sea island 
to another. 
The commonest method depends upon the wind, and on 
the barren steppes of Asia, where suitable soil is rare and 
takes much finding, some plants of the parsley kind 
make elaborate arrangements for travel. The seed- 
vessels are very large and very light—as large as a hazel- 
nut, and so light that they cannot be felt when laid on 
the hand. The winds carry these rolling along until 
they meet with damper soil, on which they remain. 
Sometimes the whole plant breaks away from the roots 
