DISPERSAL BY THE WIND 67 
shaking that they are shot or jerked out and scattered 
broadcast. 
Tt should be noted that for a great many plants 
whose fruits open for the liberation of the seeds, 
dehiscence does not take place in wet weather, but 
only when the parts concerned are quite dry, and there 
are many species which do better than this, for their 
fruits, after having opened in the dry, close up again 
in wet weather, or when the air is very damp, and the 
seeds which they still contain are thus protected from 
being clogged by the water which might otherwise 
gain admittance. 
The student should always note these points, 
testing the fruits of the species with which he is 
engaged: he will find instances of closing in the 
families, among others, to which the Poppies, the 
Ragged Robin, the Bellflowers and the Snapdragon 
belong respectively. Such observations should be 
made whenever possible on freshly opened fruits, 
as the power seems to be sometimes shortlived owing 
to abrasion or injury of the tissue concerned. 
There is, again, a small number of plants of quite 
peculiar interest in that, when wetted, their seeds 
emit a mucilage which causes them to adhere to dead 
leaves and other débris; only a few instances have 
been recorded so far from our own F lora, but, fortu- 
nately, they include two of our commonest weeds—the 
Shepherd’s-purse and the Groundsel, whose parachute 
has already been noted—so the reader can very easily 
satisfy himself by experiment, and perhaps make 
desirable additions to the records. 
Considerable care, however, is necessary when 
testing seeds for adhesiveness so as to be quite sure 
that it is not the leaf that adheres to the seed instead 
