188 Pla7it Biology 



for photosynthesis purposes. The water storage cells are large and empty 

 and have openings to the outside. Sphagnum can absorb water up to 

 twenty times its weight. 



Depending on the species, male antheridia and female archegonia may 

 be present on the same plant (but different branches) or on different 

 plants. The fertilized egg (zygote) develops into a sporophyte which has 

 a base embedded in the gametophyte, a short stalklike seta, and an en- 

 larged capsule. Because of the short seta, the gametophyte develops a 

 structure known as the pseudopodium (su do -po' di um) (Gr. pseudes, 

 false; pous, foot) at the base of the foot in order to elevate the spore- 

 producing capsule above the gametophyte. Alternation of generatio?is 

 similar to that described above takes place. Unlike Polytrichum, when 

 a spore germinates, it forms a thin, lobed, platelike prothallus (''proto- 

 nema"). Sphagnum may frequently reproduce by fragmentation. 



Sphagnum and other mosses grow on the edges of ponds and lakes 

 where they may gradually fill in the entire body of water. During this 

 process of filling in there may be masses of floating mosses. The water 

 of such bogs is apparently antiseptic because many things have been 

 preserved for years in such bog water. This antiseptic property is utilized 

 when Sphagnum is used for surgical dressings. In addition, the water 

 absorption properties are useful in this connection. 



Sphagnum is also utilized in gardening to keep the soil porous and 

 to increase the water-retaining capacity. Because of the water-holding 

 abilities, it is used by florists in packing cut flowers, in the development 

 of seedlings, etc. Sphagnum and other mosses have accumulated in bogs 

 and swamps in the past where they have slowly decomposed and become 

 compacted and carbonized. This process has produced peat which is a 

 valuable fuel. Vast deposits of peat in the United States could be used 

 in place of coal. 



LIVERWORTS 



1. Marchantia (mar -kan' shi a) (after the French botanist. Mar- 

 chant, who died in 1678) is the genus to which belong the fiat, lobed, 

 thalloid liverworts commonly found prostrate on moist rocks and soil 

 along streams. These plants are called liverworts because of their 

 fancied resemblance to the lobed liver of higher animals. 



The surface of the branched thallus body possesses rhomboidal areas, 

 each of which has a pore in its center for the exchange of gases. Inter- 

 nally, the thallus has air chambers and columns of cells containing chloro- 



