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 Pleurococcus (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 algse 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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