LIFE HISTORY OF A FERN 17 



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. 17). 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. 18). 



10. Dispersal of Spores. After the spores are mature 

 the essential need is that they become dispersed, so that 

 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 

 very small percentage of them would be able to develop 

 into new plants. When the spores are ripe the spore-case 

 opens, and by various movements the spores are expelled, 

 often to a considerable distance; by wind and other 

 agencies they may be carried still further from the parent 

 plant. 



11. Germination of Spores. After dispersal, and under 

 favoring conditions of temperature, moisture and light 

 the spore begins to absorb water, and soon commences 

 to grow. As the internal pressure increases, the walls of 

 the spore are burst apart, and a tiny tube, the germ-tube 

 or protonema (first thread), begins to develop. This 

 process is germination. Shortly, near the wall of the spore, 

 a smaller, slender tube develops as a branch of the germ- 

 tube (Fig. 19). This is the first of innumerable root-like 

 bodies, or rhizoids, which will help to hold the new plant 



