THE BRYOPHYTA 143 



spores are not all scattered at once ; the dissemination 

 is regulated by the teeth of the peristome, which, when 

 the air is wet, completely close the mouth of the 

 capsule, only allowing the spores to escape in dry 

 weather. The spores themselves contain abundant 

 chlorophyll, and also have a reserve of oil which 

 serves to provide material for germination. When this 

 takes place, the spore does not at once give rise to a 

 Moss plant,but first of all produces a branched filamentous 

 growth of very simple structure, much resembling some 

 of the simpler plants (Algai), as we shall find later on. 

 This filamentous condition of the young Moss, which 

 thus forms the first stage of the oophyte generation, is 

 called the protonema (see Fig. 59). The spore gener- 

 ally sends out filaments in two directions ; one remains 

 green and creeps along the surface of the ground, the 

 other loses its chlorophyll and becomes the first rhizoid. 

 The filaments grow in each case by an apical cell ; 

 they branch freely but remain one cell only in thick- 

 ness ; often the protonema develops to a great extent, 

 forming a tangled green felt, which may cover several 

 square inches of ground. The young Moss plants arise 

 from the protonema as lateral buds (see Fig. 59, k). 

 A cell of the protonema gives rise to a branch ; the 

 branch divides by inclined walls so as to form a 

 tetrahedral apical cell, and as soon as this has taken 

 place regular segmentation begins, and the leafy Moss 

 plant is soon built up. The first leaves are simpler 

 than those of the more mature plant, and may be 

 destitute of a midrib. 



The protonema which we have just described is 

 formed directly from the spore, and is therefore called 

 primary protonema. It may also arise in a secondary 



