298 STRUCTURE OF SPHAGNUM 



and animals that fall into these bogs may only partly decay and 

 remain for ages in a wonderful state of preservation as is shown 

 by the recovery of skeletons of animals and clothing of men that 

 belonged to a 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 im- 

 portant fuel in Europe and the vast deposits of it in this country 

 will doubtless be utilized in the future. It has been recently 

 shown that the material of some of these bogs is of great value 

 as a source of pulp for paper. 



(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 commercial 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 



