CHAPTER IV 
Geographical Distribution 
GRASSES are at once the most abundant and the most universally 
distributed of all flowering plants ; there is no hiatus in their world- 
wide diffusion ; they flourish in every part of the earth where vege- 
tation can exist. The Graminee number 3,100-3,200 species, and 
are therefore among the largest families of flowering plants, ranking 
only after the Composite, 10,000 species, and the Orchidee and 
Leguminosa@, about half as numerous. The number of species of 
grasses, in proportion to the total number of species of flowering 
plants, is about ¢ in arctic and antarctic regions, about 7; in 
temperate climates, and from ~; to j; within the tropics ; 
but in countless myriads of individuals the grasses far surpass 
every other order, and growing ez masse as they commonly do, 
they constitute in many, if not most, regions the grand character- 
istic feature of the flora. Treeless, grassy plains are estimated to 
occupy rather more than one-fourth of the land-surface of the 
lobe, 
e The cooler parts of the north temperate zone are characterized 
by dwarf tender grasses, with short, slender leaves, forming a close 
continuous turf. In low fertile plains the culms grow for the most 
part 2-3 feet high ; on hillsides and elevated tablelands with a 
poorer soil, they are much shorter ; in shady and swampy situa- 
tions they rise to 4-6 feet, and have proportionately larger foliage. 
Where an insular climate prevails, with frequent rains, a humid 
atmosphere and temperate summer heat, and in mountainous 
regions whose slopes and valleys are irrigated throughout the 
warm months by melting snow, the earth is covered with a thick 
matted, velvety, evergreen sward. In no part of the world do we 
find such a beautiful “carpet of living green” as in the western 
parts of Great Britain, the “Emerald Isle” and the alpine pastures 
of Middle Europe. Under a continental climate of scorching 
summer heat and low winter temperature, the grasses do not form 
such a compact sod, and the green turf which clothes the ground 
in spring soon becomes brown and withered; the grassy expanse 
of the Kirghiz steppes is then transformed into a dusty desert, and the 
dry western plains of North America, which have a more luxuriant 
but equally sun-dried turf, are subject to prairie-fires. The eastern 
prairies of the Mississippi plain, with a more abundant rainfall and 
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