CHAPTER XXIX 
HOW PLANTS ARE SCATTERED AND PROPAGATED 
441. Means of Propagation among Cryptogams. — Some 
of the highest cryptogams, as the ferns, spread freely by 
means of their creeping rootstocks, and the gardener who 
wishes quickly to get large, strong ferns often finds it the 
easiest plan to cut to pieces and reset the rootstocks of a 
well-established plant. Some ferns also grow readily from 
bulblets produced on the fronds. In the walking fern 
the tip of the frond roots and begins a new plant. Most 
flowerless plants, however, are reproduced either by a 
process of fission, as in Pleurococeus (Sect. 278), Diatoms 
(Sect. 271), Bacteria (Sect. 266), and many other groups, 
or by some kind of spore (Sect. 259). The spore is 
usually so small an object that it is carried with the great- 
est ease by currents of water or of air, as the case may 
be, so that it is no sooner liberated than it is swept away, 
often to a very distant locality, where it can grow and not 
be interfered with by too many neighbors of its own kind. 
Thus spores of any of the marine alge are certainly carried 
thousands of miles by ocean currents, and spores of tree 
ferns may be blown great distances from one oceanic island 
to another, or the spore contents of a puff-ball might travel 
on the wind half the breadth of a continent. 
442. Dispersal of Seed-Plants by Roots and Rootstocks. — 
The student has learned (in Chapters IV and V) that 
roots and underground stems of many kinds may serve to 
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