CuHaprer VII. 
THE STRUGGLE FOR EXISTENCE. 
Among plants as well as animals there is constant 
competition for food and place. If a highly cultivated 
garden be left only for a month or two it will be found 
that it has been invaded by a growth of hardy, vigorous 
weeds that have almost choked out the original 
occupants of the soil. These weeds are merely plants, 
which, beeause of certain peculiarities of habit and 
structure, have an advantage over those they have 
ousted. The nature of the vegetation covering any 
uncultivated area depends on the result of the 
‘Struggle for Existence,’’ in which the victory is to 
the individuals or species whose equipment is_ best 
suited to the particular environment. In this struggle, 
environment exercises a kind of ‘‘Natural Selection’? 
resulting in the ‘‘Survival of the Fittest’? and the 
*‘Klmination of the Unfit.’’ 
The weight of evidence goes to show that all the 
variety of plants that to-day covers and beautifies the 
earth has had its origin in certain extremely simple 
forms. The small green speck of protoplasm that eon- 
stitutes the primitive plant has given rise to moss and 
fern, to grass, shrub, and tree. The earliest one-celled 
plant multiplied by simple division, a single individual 
splitting in halves and thus forming two. It might 
happen, in the course of ages, that, in rare instances, 
instead of separating, the cells thus formed by division 
would cohere and produce a two-celled organism. By 
similar means individuals containing many cells might 
come into existence. The next step would be when 
there arose differences in shape and structure of 
individual cells that formed the organism. If these 
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