470 FACTORS OF ORGANIC EVOLUTION. 



animal creation leaves its centrogenio arrangement early in its own 

 time scale, the plant creation assumes such arrangement at a compara- 

 tively late epoch in its time scale. 



Perhaps the best illustration which I can bring you of the origin of 

 the unlike by means of environmental conditions and the survival of 

 some of this unlikeness in the battle for life, is the development of the 

 winter quiescence of plants. What means all this bursting verdure of 

 the liquid April days? Why this annually returning miracle of the 

 sudden expansion of the leaf and flower from the lifeless twigs'? Were 

 plants always sof Were they designed to pass so much of their exist- 

 ence in the quiescent and passive condition? No. The first plants 

 had no well-defined cycles, and they were born to live, not to die. 

 There were probably no alternations of seasons in the primordial world. 

 Day alternated with night, but month succeeded month in almost 

 unbroken sameness age after age. As late as the Carboniferous time, 

 according to Dana, the globe " was nowhere colder than the modern 

 temperate zone, or below a mean temperature of 60° F." The earth 

 had become wonderfully diverse by the close of the Cretaceous time, 

 and the cycads and their kin retreated from the poles. Plants grew 

 the year round 5 and as physical conditions became diverse and the 

 conflict of existence increased, the older and the weaker died. So a 

 limit to duration, that is, death, became impressed upon the individuals 

 of the creation; for death, as seen by the evolutionist, is not an original 

 property of life matter, but is an acquired character, a result of the 

 survival of the fittest. The earth was perhaps ages old, even after life 

 began, before it ever saw a natural death ; but without death all things 

 must have finally come to a standstill. When it became possible to 

 sweep away the old types, opj)ortunity was left for new ones; and so 

 the ascent must continue so long as physical conditions, which are not 

 absolutely prohibiti\;e of life, shall become unlike. 



Species have acquired different degrees of longevity, the same as 

 they have acquired different sizes and shapes and habits — by adapta- 

 tion to their conditions of life. Annual plants comprise about half of 

 the vegetable kingdom, and these are probably all specializations of 

 comparatively late time. Probably the greater part of them were origi- 

 nally adaptations to shortening periods of growth; that is, to seasonal 

 changes. The gardener, by forceful cultivation and by transferring 

 plants toward the poles, is able to make annuals of perennials. IsTow, 

 a true annual is a plant which normally ripens its seeds and dies before 

 the coming of frost. Many of our garden plants are annuals only 

 because they are killed by frost. They naturally have a longer season 

 than our climate will admit, and some of them are true perennials in 

 their native homes. These plants are, with us, plur annuals, and 

 among them are the tomato, red pepper, eggplant, potato, castor 

 bean, cotton, lima bean, and many others. But there are some varieties 

 of potatoes and other plants which have now developed into true 



