104 BOTANY. 



surface of the liverworts, which fasten it firmly to the ground. 

 By and by, if our culture has been successful, we may find 

 attached to some of the larger of these, little fern plants grow- 

 ing from the under side of the prothallia, and attached to the 

 ground by a delicate root. As the little plant becomes larger 

 the prothallium dies, leaving it attached to the ground as an 

 independent plant, which after a time bears the spores. 



In choosing spores for germination it is best to select those 

 of large size and containing abundant chlorophyll, as they ger- 

 minate more readily. Especially favorable for this purpose 

 are the spores of the ostrich fern ( Onoclea struthiopteris) (Fig. 

 70, J, J)j or the sensitive fern (0. sensibilis). Another com- 

 mon and readily grown species is the lady fern (Asplenium filix- 

 foemina) (Fig. 70, H). The spores of most ferns retain their 

 vitality for many months, and hence can be kept dry until 

 wanted. 



The first stages of germination may be readily seen by sowing the 

 spores in water, where, under favorable circumstances, they will begin to 

 grow within three or four days. The outer, dry, brown coat of the spore 

 is first ruptured, and often completely thrown off by the swelling of the 

 spore contents. Below this is a second colorless membrane which is also 

 ruptured, but remains attached to the spore. Through the orifice in the 

 second coat, the inner delicate membrane protrudes in the form of a 

 nearly colorless papilla which rapidly elongates and becomes separated 

 from the body of the spore by a partition, constituting the first root hair 

 (Fig. 66, B, (7, r). The body of the spore containing most of the chloro- 

 phyll elongates more slowly, and divides by a series of transverse walls 

 so as to form a short row of cells, resembling in structure some of the 

 simpler algae (C). 



In order to follow the development furtner, spores must be sown upon 

 earth, as they do not develop normally in water beyond this stage. 



In studying plants grown on earth, they should be carefully removed 

 and washed in a drop of water so as to remove, as far as possible, any 

 adherent particles, and then may be mounted in water for microscopic 

 examination. 



In most cases, after three or four cross-walls are formed, two walls 

 arise in the end cell so inclined as to enclose a wedge-shaped cell (a) from 

 which are cut off two series of segments by walls directed alternately 



