284 STRUCTURE OF SPHAGNUM 



prehistoric period. It is because of this condition that the bog 

 mosses are of great economic importance. The dead portions 

 of the moss plants, as well as that of the associated plants, do 

 not entirely decay, and consequently there is slowly formed a 

 compact mass of material rich in carbon. This is cut or pressed 

 into blocks, forming peat. This material is an important fuel in 

 Europe and the vast deposits of it in this country will doubtless 

 be utilized in the future. 



(a) The Structure and Reproduction of Sphagnum. — The leaves 

 of the bog moss are arranged in compact spirals around the 

 stems and consist of a single layer of cells as in the leafy hepatics 

 (Fig. 202, B). These cells, however, are of two kinds, large 

 and empty cells with spirally thickened walls which are generally 

 perforated with small pores and very narrow cells containing 

 chlorophyll. This distribution of the cells explains the pale- 

 green color characteristic of the sphagnums. Large and spirally 

 marked cells, similar to those of the leaf, may also occur in the 

 cortex of the stem. The closely packed leaves enable the bog 

 mosses to take up water like a sponge and the sphagnums are 

 of considerable commerical value for this reason, being exten- 

 sively employed by horticulturists to keep plants moist during 

 shipment. They are also used extensively in stables in place 

 of straw and they render them almost odorless owing to their 

 absorption of liquids and gases. Perhaps these large cells may 

 serve as floats, enabling the plant to bridge over ponds and they 

 may enable the plant to endure the acid waters in which these 

 plants grow. In this connection, it is noteworthy that rhizoids 

 are entirely lacking and that water and other substances are 

 absorbed by the outer cells of the stems and by certain branches 

 which hang down in wick-like strands close to the main stem 

 (Fig. 201). 



The antheridia and archegonia are developed much as in the 

 leafy hepatics, the former organs appearing as stalked bodies 

 in the axils of the leaves on short cone-like branches and the 

 archegonia originate on the tips of short branches. The gameto- 

 spore germinates very much as in Anthoceros (Fig. 203, 6). 

 It does not, however, have as prolonged a growth, and at ma- 



