1896.] ^^^ [Bailey. 



But as a mere feeding organ, the root requires no fibrous structure. It 

 is still a hold-fast or grapple and its mechanical tissue has developed 

 enormously, along with that of the stem, in order to preserve the plant 

 against the strain of the moving elements and to maintain its erectness in 

 aerial life. When this self-poised epoch arrives, the vegetable world be- 

 gins its definite and steady ascent in ceutrogenic form. Whilst the ani- 

 mal creation leaves its centrogenic arrangement earlj' in its own time- 

 scale, the plant creation assumes such arrangement at a comparatively 

 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 expan- 

 sion of the leaf and flower from the lifeless twigs ? Were plants always 

 so ? Were they designed to pass so much of their existence in the quies- 

 cent and passive condition ? No. The first ph'ints 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 tem- 

 perature 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 ; 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 indi- 

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

 to sweep away the old types, opportunity was left for new ones ; and so 

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

 absolutely prohibitive of life, shall become unlike. 



Species have acquired different degrees of longevity, the same as they 

 have acquired difterent sizes and shapes and habits — by adaptation 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 originally adaptations to 

 shortening periods of growth, that is, to seasonal changes. The gardener, 

 by forceful cultivation and by transferring plants towards the poles, is 

 able to make annuals of perennials. Now, 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. Thej^ 

 naturally have a longer season than our climate will admit, and some of 



PKOC. AMER. PHILOS. SOC. XXXV. 150. N. PRINTED JULY 9, 1896. 



