IMPORTANCE OF DISPERSAL 49 
In the plant world, the higher forms, with very few 
exceptions, spend their lives attached to one spot, 
like sea-anemones, deriving their food-supply from 
the air and from the soil; but they similarly are given 
the opportunity, after birth, of migrating. In our 
familiar wild flowers, for instance, the young plant, at 
an early stage of its existence, while it is still minute, 
becomes covered with a coat often of very resistant 
qualities, and is then cast loose by the parent in the 
form of seed, mostly in great numbers, to achieve 
what travels it can before it takes root and settles 
down, like its parent before it, to a humdrum exist- 
ence. In the Cryptogams, or so-called Flowerless 
Plants, this temporary compression of the organism 
into very narrow limits suitable for easy dispersal 
takes place at a different period in the life cycle, 
but for mechanical purposes the results are similar. 
Minute bodies, or spores (much smaller than the seeds 
of the Seed Plants), are cast loose by the parent 
often in vast numbers, and eventually settle down and 
reproduce the species. In many of the lower aquatic 
plants these spores are provided with means of loco- 
motion in the form of a tail-like appendage, which by 
its movement propels the germs through the water, 
giving them the same advantage which is possessed 
by the young of many of the sedentary animals. 
The opportunity for migration thus offered to 
sedentary plants once at least in each cycle is of very 
great importance. A plant, living on one spot and 
drawing, from that portion of the soil which its roots 
can reach, certain mineral salts essential for its con- 
tinued growth, tends to exhaust the available supply 
of these materials, and the succeeding generation 
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