138 MANUAL OF NATURE STUDY. 



causes tlie rock to decay and crumble into dust or soil, 

 sufficient to give the moss-spores lodgment. So moss 

 takes tke place of lichens j ust as soon as the latter has 

 prepared the soil for the support of the moss forest. 

 But moss will grow upon damp soil, wherever shaded 

 and supplied with proper amount of heat. In fact, 

 it does not require a great deal of heat or moisture 

 to support some kinds of moss, as it is well known 

 that great quantities of moss grow in the cold re- 

 gions of the north where few other plants can exist. 

 It will also do well upon dry knolls. Let the child- 

 ren state where they have seen moss, and name 

 some things peculiar to its nature. The Pigeon- 

 Wheat moss is perhaps the commonest kind and 

 can be found in great abundance by the children 

 upon almost any side hill and often between the 

 bricks of walks where the place is damp and shaded. 

 The Pigeon- Wheat moss is known by its long 

 pedicel bearing on its apex a capsule containing 

 spores which, when ripe, are threwn out to be 

 scattered by the wind the same as fern spores. 



These spores are no more the nature of seeds 

 than fern spores are seeds, or puff-ball dust is seed. 

 All seeds contain an embryo and food supply, the 

 latter being either within or without the embryo ; 

 but the spores contain no embryo. They give 

 rise to green web-like threads, called protonema, 

 which have no roots, but cling very closely 



