LIFE HISTORY OF A FERN 1 63 



whether, in the evolutionary development of the plant 

 kingdom, through long geological ages, foliage-leaves have 

 in general originated by the sterilization of spore-bearing 

 organs. 



149. Vegetative Multiplication. — In addition to re- 

 production by spores, ferns may also be propagated vege- 

 tatively in at least four ways. By one of these methods, 

 the rhizome is cut into several pieces, and from every 



Fig. 123. — A Boston fern (Nephrolepis), reproducing vegetatively by 

 means of runners or stolons. The parent plant is in the round pot. (After 

 R. C. Benedict.) 



piece that contains a bud a new plant will develop. By 

 the second method, the plant is propagated by means of 

 bulbils^ which occur on the foliage-leaves of several 

 species. In the fern Tectoria cicutaria, bulbils occur on 

 both the upper and under sides of the leaf (Fig. 121). These 

 bulbils fall to the ground, and under suitable conditions of 

 light, moisture, and temperature give rise to new fern- 

 plants. One of the ferns native to the eastern United States 



