LIFE HISTORY OF A FERN 163 
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. (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. 1 2 1 ) . 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 
