Il] HYDROPHYTES AND MESOPHYTES 37 



property largely taken advantage of in certain forest 

 operations. 



Other grasses, particularly annual species, show their 

 adaptation to xerophytic habits by forming bulbous store- 

 houses at the base of the culms — e.g. Phleum arenarium. 



Some GraminaceiJe are hydrophytes, such as Arundo, 

 Glyceria, &c., with large intercellular spaces in their tissues; 

 while many species— e.g. Aira cwspitosa, Agrostis canina, 

 Molinia ccerulea — grow on wet moor-lands, forming peren- 

 nial tufts, with or without creeping rhizomes. 



The mesophyte grasses are especially characteristic of 

 what may be termed carpets — a lawn is a good example 

 on a small scale, though of course we must remember 

 that here the struggle for existence has been artificially 

 interfered with more or less. Such carpets consist of the 

 densely interwoven rootlets and rhizomes forming sod, and 

 contain much humus from the accumulated debris of former 

 years. These grass-carpets may be composed of nearly 

 pure growths of a few species, or of very many different 

 grasses and other herbage.- They are common in Arctic 

 regions, on Alps, and in temperate climates generally, where 

 we know them as meadows, hay-fields, pasture and lawns. 



The Bamboos in the wider sense have a physiognomy 

 of their own, e.g. in India, and may drive out most other 

 plants and form dense undergrowths or jungle of interlaced 

 stems and leaves and thorny shoots. Similar growths 

 occur on the Andes and elsewhere in South America. In 

 some parts of India and tropical Asia the taller bamboos 

 form aggregates comparable to dense forests, and such 

 forests are common on the banks of several large tropical 



