LIFE HISTORY OF A MOSS 20I 



foot, imbedded in the tissues below, and connected with 

 the spore-case by a very short stalk (Figs. 143 and 145). 



184. The Sporoph3rte. — It will have been recognized 

 already that the simple structure just described, since it 

 bears spores, is the sporophyte stage of Sphagnum} 

 While the sporophyte is maturing, the apex of the female 

 branch elongates, forming a leafless stalk, a half inch or 

 more in length. This stalk is called the pseudo podium 

 (false foot). The development of the pseudopodium, 

 coincident with that of the sporophyte is very interest- 

 ing, and the question at once naturally arises, as to how 

 this correlation is brought about. No positive explana- 

 tion has ever been given, but it seems probable that, as the 

 sporophyte begins to develop, the cells of the foot excrete 

 some substance which stimulates the cells in which it is 

 imbedded to divide and enlarge, resulting finally in the 

 formation of the pseudopodium. The advantage of the 

 pseudopodium in facilitating the distribution of spores 

 by raising the spore-case higher into the air and well 

 above the perichaetial and other leaves, is obvious. 



The sporophyte of Sphagnum possesses no chlorophyll, 

 and consequently does not elaborate any food, obtaining 

 its entire supply from the sphagnum-plant by absorption 

 through the foot. Numerous groups of stomatal guard- 

 cells occur on the wall of the spore-case, but they have no 

 slit between them — no true stomata — and are there- 

 fore functionless. There are also, underneath the guard- 

 cells, no intercellular spaces, such as are always associated 

 with true stomata. The presence of these functionless 

 stomata is thought by some botanists to indicate that the 



^ Such simply organized sporophytes are commonly called sporogonia 

 (singular sporogonium). 



