xviii INTRODUCTION. 



exceed, two feet in length. One of the largest which our country 

 produces, is the Polytriclium commune, of which we have fre- 

 quently seen brushes made, and hassocks, used for kneeling upon 

 in churches. 



Like the Ferns, the Mosses delight chiefly in damp and shady 

 situations ; though they are by no means exclusively confined to 

 these places of growth. From beneath the Torrid Zone, we have 

 received portions of the stems of cocoa nut trees, entirely covered 

 with a rare white Moss, the Octoblepharum albidum of Hedwig, 

 and others of still more uncommon occurrence, gathered on the 

 burning sands of the deserts, in the interior of Southern Africa. 

 Upon thatched roofs, in our own country, is seen most abundantly 

 the Tortula ruralis, forming a dense mass of a yellow green, or a 

 rich brown colour, according as the plant is destitute of, or 

 furnished with, its fructification. Mosses are frequently observed to 

 grow in places that would hardly afford nourishment to any other 

 kind of plant. The tops of the driest walls are covered with the 

 little Grimmia pulvinata, whose leaves are tipped with long white 

 pellucid hairs, and whose capsules, by the curvature of their foot- 

 stalks, are curiously buried among these leaves. In the same 

 places, and upon the sides of walls that are equally scorched and 

 barren, grows the Tortula muralis. In a hot season, these 

 Mosses, and very many others, become crisped, parched, and to 

 all appearance, lifeless ; but if only a slight shower falls, or a sum- 

 mer's evening dew, the most, shrivelled, in a few minutes, are 

 seen to be filled with moisture, which is indeed imbibed by them 

 with wonderful rapidity. The same phenomenon occurs with^the 

 specimens that have been gathered and preserved in a dry state in 

 the Herbarium for a century and more ; immerse these in water, 

 and they presently revive as much as if they were freshly gathered. 

 It is in moist situations that by far the greater number of species 

 are to be met with. Boggy and marshy places abound with them, 

 and they there arrive at a great size. Although the low grounds 



