30 THE GEOGRAPHY OF PLANTS. 



sents an elegant tuft of silvery hairs. Their 

 structure unfits them for weaving into any 

 fabric, but in the northern counties of England 

 and Scotland they are much used by the poor 

 for stuffing pillows. 



Bock and gravel plants. These generally 

 grow on bare rocks or dry gravel ; the cactus 

 and stonecrop tribes, many of the ferns, lichens, 

 and mosses, are examples. In the gravel which 

 is formed by the action of mountain-torrents, 

 especially at lofty elevations, are found some 

 peculiar plants, such as Ranunculus glacialis, 

 which adorns heights otherwise barren, and 

 bordering on the regions of perpetual snow. 

 Here we may also mention mountain plants, 

 which, as their name implies, grow especially 

 on mountain ranges. Their number is very 

 great, though numbers of species which are 

 sometimes found on mountains cannot properly 

 be said to be mountain plants, as will be seen 

 when we come to speak of the influence of 

 altitude. One example will suffice at present. 

 On the Himalayan mountains, at the height of 

 from five thousand to nine thousand feet above 

 the level of the sea, the vegetation assumes a 

 perfectly European aspect. Though situated in 

 a tropical country, the great elevation produces 

 such a diminution of temperature, that at that 

 height the climate resembles that of our own 

 country, and the plants are also very similar. 

 The dandelion, the ivy, our common meadow 

 grasses, (Poa annua and Alopecurus genicu 

 atus,) cleavers, (Galium aparine,)imd a number 



