Groups into Which Plants Naturally Fall 455 



fine-leafy, low stems growing densely-compacted together, with 

 slender-stalked spore cases standing out from their ^ops. Mo^t 

 striking of them all are the Peat-mosses {Sphagnum), which form 

 in wet northern climates the great bogs such as, doubtless, 

 long ago, played a part in the origination of the coal beds. In 

 size, the Moss-plants are all low, not over a few inches in height, 

 and they have no parts underground excepting some water- 

 absorbing hairs, — which fact explains why all Mosses are so 

 easily stripped from the ground. Their cellular anatomy in the 

 best developed forms includes a waterproof epidermis with 

 stomata, and intercellular spaces, — features correlated with their 

 air-living habit; but otherwise the tissues are little more special^ 

 ized than in Algae, and their lack of a particular strengthening 

 and conducting system explains why they never can rise much 

 above the ground. In color they are typically green, often intense 

 in its shade, from the presence of chlorophyll with which they all 

 make their own food, though the greenness is often obscured, 

 especially in those of exposed places, by screens of red or brown 

 pigments which are doubtless a protection to the protoplasm 

 against the injurious action of untempered light. Their reproduc- 

 tion is partly by dust-like spores, scattered from exposed spore 

 cases by the wind, and partly by fertilization, effected by the 

 fusion of a free-swimming male cell with a well-enclosed and pro- 

 tected egg-cell. And it is a fact of great interest to Botanists 

 that fertilization and the production of spores alternate regularly 

 with one another in two separate generations, whereby hangs a 

 remarkable tale, too special for relation in this place, and of 

 which, moreover, the exact point is still tantalizingly elusive. 

 As to the numbers of the Moss-plants, some seventeen thousand 

 kinds have been described, and doubtless a good many are still to 

 be found. 



Of course there are plants which look like this group, but are 

 not. Thus there is a ''Liverwort" which is a Flowering Plant 

 (the Hepatica), while the ''Spanish Moss," of the Oaks in the 



