HOW PLANTS SPREAD AND MULTIPLY 41 
this mechanism is given by a plant which you may often 
see in a garden, the Egyptian Balsam. When the seed- 
vessels are ripe, and just touched with a finger, the strain 
of the elastic tissue within becomes too great, the sides 
fly out like the ribs of a collapsed umbrella, and the seeds 
are shot vigorously all about the garden, with the result 
of Egyptian balsams everywhere 
—even where not wanted—next 
summer. A smaller plant ex- 
hibits the same performance, the 
Brown Sorrel, and is equally rapid 
in covering all the available space. 
It has brown leaves, divided into 
three like clover, yellow flowers, 
and long, spiky seed - vessels. 
Brush your hand over one of 
these, and you will hear a furious 
spitting and see little mahogany- 
coloured seeds flying in all directions. This does not fly 
open like the balsam, but is more like a close-folded um- 
brella, where the silk suddenly splits along all the folds. 
If, again, you go on a hot afternoon near a bed of 
golden furze, you may hear the pods popping away with 
almost military fervour. As to the distance, such plants 
as we have in England are content with a yard or two at 
best, but there is a tropical plant, called Bauhinia, which 
has been known to fling its seeds eighteen or twenty yards, 
with a really effective explosion. It is obvious, too, that 
if an animal sets the machinery in motion, the seeds may 
stick in its fur, or possibly in its clothes, and thus 
manage quite a long journey. | 
Akin to these are the creeping and hopping seeds, 
examples of which may be found among the grasses. 
EGYPTIAN BALSAM 
SEED-VESSELS 
