Explanatory Notes on Mosses 497 



selves to dry up in hot weather and being ever ready to swell 

 out again when it rains. 



It is customary to say that mosses have no roots, but this is 

 almost an abuse of the English language. They have roots 

 which are just as true to their duties as are those of the oak. 

 Those duties, however, do not include the taking up of any- 

 thing, water or other, from the soil in which they grow, but 

 concern only the purpose of fixation. The proper mode of 

 expression should be that the roots of mosses are, like their 

 stems, destitute of sap-tubes. 



The family of mosses is divided into three groups, under 

 the names of Liverworts, Sphagnums and True Mosses. The 

 use of such words as "true" and "false" in reference to 

 natural objects might, perhaps, be suitably discouraged, for 

 they are either meaningless or worse. In the present instance 

 it might be better to speak of Liverwort mosses, Bog-mosses 

 and Urn-mosses. 



The following memoranda, which are in part recapitulation 

 of what has been said, may be useful : — 



(1) Mosses have no tubular arrangements for the con- 

 veyance of sap or water from part to part. Thus they are 

 said to be " non-vascular " plants. 



(2) Their roots serve to fix them where they grow, but do 

 not absorb anything from the soil, as do the roots of flowering 

 plants. It is customary, therefore, to say that mosses have 

 no true roots. This is clearly a question of definition of the 

 word. 



(3) As mosses are not dependent upon their roots for a 

 supply of food, but derive the latter from the air, their upper 

 parts may continue to live and grow, long after the root and 

 even large portions of the stem, with its leaves, are dead. 



(4) The leaves and stems of mosses are of very simple 

 structure, consisting of cells, but little modified, united 

 together. They have no bark or epidermis. 



(5) Whilst mosses are incapable of taking up moisture 

 by their roots into the interior of their stems,, they have a 



