136 THE NATURE AND WORK OF PLANTS 



reddish cigar-shaped bulbUs in the upper axils of the 

 stems, which consist of a thickened branch sheathed 

 by blunt scales. These structures drop from the 

 plant in the autumn, and those which fall in the 

 water, or those which are covered up by falling 

 leaves, escape frost and germinate in the following 

 spring, reproducing the plant. Those that drop into 

 the water may be carried away by currents, and 

 thus spread the species into unoccupied territory. 



Cystopteris (C. bulbifera), a common fern, forms 

 numerous bulblets on the lower surfaces of the mid- 

 ribs, which drop off in the autumn and germinate in 

 the spring. 



186. Division of the body by the death of part of 

 it. — Some of the liverworts, club-mosses, ferns, and 

 many of the seed plants have creeping underground 

 stems which branch in the form of a letter Y. By 

 the death of the older part of the stem, representing 

 the base of the Y, the two branches are left as 

 separate plants. These extend, branch, and divide in 

 the same manner. Note this process in the com- 

 mon liverwort [Marchantia, or Conocephalus), in the 

 rhizomes of the fern and club-moss. It may be seen 

 also in the creeping grasses. 



