16 MISSISSIPPI STATE GEOLOGICAL SURVEY [Bull. 
forms leaf functions; some water plants have no roots, but in 
these absorption of food-laden moisture takes place through 
the whole plant body immersed in water; a considerable num- 
ber of plants of otherwise high organization, called parasites, 
have adopted the stealthy habit of living entirely, or partly, 
upon the elaborated food drawn from other plants, and as a 
consequence they usually skulk in darkened places, like the 
assassins that they are, and hence are pale spectres that have 
lost their green tissue, through which other more normal spe- 
cies rejoice in the sunlight, and like diligent housewives, go 
about their legitimate duties. 
Aside from these abnormal developments of higher groups 
of plants to meet unusual conditions of living, there is a whole 
horde of lowly organized and imperfectly differentiated forms 
of plant life which have neither leaf, stem, nor root, properly 
so-called. These little forms are for the most part aquatic in 
habit, and by far the greater number are microscopic in size; 
some of the higher groups, however, as the, liver-worts 
are larger and live attached to damp rocks, tree trunks or to 
wet soil. While in these low groups no specialization of parts 
corresponding to those of the higher plants has taken place, 
they perform all the functions of the higher plants, any part 
of the plant body being able to assume any function necessary 
to the plant economy—a condition which may be likened to 
the conditions of primitive human society, where each man 
was in turn his own butcher, carpenter, shoemaker, and barber. 
Plants Universally Distributed.—That plant life is very 
unequally distributed over the earth is a matter of common 
knowledge. The tropical forests of Brazil present a pro-. 
nounced difference from the pampas of Argentina or the 
Great Plains of North America, and a still more striking con- 
trast to the barren wastes of the Sahara Desert. The great 
broad-leafed forests of temperate North America are succeeded 
to the north by the equally extensive Canadian and Hudsonian 
pine, fir, and spruce forests; which in their turn, as they ap- 
proach the pole, give way to the treeless, moss-covered Arctic 
tundra. 
