2 NUMBERS AND USES [CH. 
Although in the actual number of species the Grass 
family is by no means the largest in the vegetable 
kingdom, for there are far more Composites or Orchids, 
the curious sign of success in the struggle for existence 
comes out in grasses in that the number of individuals 
far transcends those of any other group, and that they 
have taken possession of all parts of the earth’s surface. 
Some species are cosmopolitan—e.g. our common Reed, 
Arundo Phragmites; while others—e.g. several of our 
native species of Festuca and Poa—are equally common in 
both hemispheres. On the whole the Tropics afford most 
species and fewest individuals, and the temperate regions 
most individuals. 
Considering their multifarious uses as fodder and food, 
for brewing, weaving, building and a thousand other 
purposes, it 1s perhaps not too much to say that if every 
other species of plant were displaced by grasses of all 
kinds—as many indeed gradually are—man would still be 
able to supply his chief needs from them. 
The profound significance of the grass-carpet of the 
earth, however, comes out most clearly when we realise 
the enormous amounts of energy daily stored uj in the 
countless myriads of green blades as they fix their carbon. 
By decomposing the carbon-dioxide of the air in their 
chlorophyll apparatus by the action of the radiant energy 
of the sun, they build up starches and sugars and other 
plant-substances, which are then consumed and turned 
into flesh by our cattle and sheep and other herbivorous 
animals, and so furnish us with food. The whole theory 
of agriculture turns on this pivot, and the by no means 
