356 



BOTANY OF THE LIVING PLANT 



commonly makes its appearance there, though none of the species 

 may be seen in the near neighbourhood. But occasionally the 

 method of spread is more precise. Thus the spores of some Mosses 

 are sticky, and readily carried by insects. This is so with the 

 dung-infecting Splachnum, the agent of its spread being the dung-fly. 

 Scattered in one way or another, the spore germinates in presence of 

 moisture, giving rise to filaments, which as they grow are partitioned 

 into cells, and soon branch. Some of the branches are exposed at the 

 surface of the soil, and develop chlorophyll. Others burrowing into 



Fig. 298. 



a, b, c, germination of Moss-spores to form protonema. t^= formation of a bud 

 laterally upon the protonema. e= diagrammatic plan of the segmentations of d, as 

 seen from above. (After H. Miiller.) 



the soil are colourless, or have brownish walls ; they serve as rhizoids • 

 (Fig. 298). The filamentous system thus produced is called protonema, > 

 and the formation of Moss-Plants is regularly preluded by this filameii- , 

 tous stage. If grown in dim light it may increase indefinitely, but 

 with full exposure it sooner or later forms Moss-plants. These arise 

 as buds, each taking the place of a branch of the protonema, and, 

 may be held to be a condensed form of it. The segmentation of the ' 

 bud is from an initial cell, by walls with rather more than 120 degrees 

 of divergence, as shown in ground plan (Fig. 298, d, e). Each segment- 

 gives rise to a leaf of the Moss-Plant, borne on the upward-growing] 

 stem. But this does not check the growth of the protonema, whichf 

 may extend indefinitely. Branches from the rhizoids may anywhere 



I 



