164 STRUCTURE AND LIFE HISTORIES 
(Cystopteris bulbifera) received its specific name from the 
fact that it bears bulbils. A third method is illustrated 
in the very interesting "walking fern" (Camptosorus 
rhizophyllus) , where the tips of the long acuminate leaves 
rest upon the moist ground, take root, and develop an 
entire new plant at the distance of the leaf's length from 
the parent fern (Fig. 122). The result of several repeti- 
tions of this suggested the common name "walking fern." 
A fourth method is by means of stolons or "runners" 
(Fig. 123). 
150. Dispersal of Spores. After the spores are mature 
the essential need is that they become dispersed, so that 
FIG. 124. Tips of two sporophylls of the fern, Drynaria meyeniana, 
showing the large marginal sori. The black dots adjacent to the leaf-tips 
are spores projected onto white paper by the snapping of the sporangia. 
The specimens were covered with a bell-jar. 
they may find favorable conditions of moisture, tem- 
perature, light, and soil for development; for, with rare 
exceptions, such conditions do not obtain within the 
spore-case. Moreover, if the spores remained within the 
sporangia they would be so greatly crowded that only a 
