102 



THE 



[vol. n 



huma 



no consecutive weather records have been kept, but I was assured that the 

 average winter temperature is several degrees warmer tlian that of the 

 open plains. Cattle are wintered in the canyons without feeding or arti- 

 ficial shelter and without losses such as occur in the open country above. 

 Based upon a study of the wild life, principally the fauna, the United States 



Lo 



ding 



zone. 



accous 



The plants peculiar to the canyons appear to be emigrants from various 

 sources. Most of them have doubtless advanced gradually or been trans- 

 ported directly over wide intervening distances by various agencies from the 

 Edwards Plateau region to the south ; some appear to have come in by way 

 of the upper Pecos valley from extreme southwestern Texas, amongst them 

 such woody forms as Glossopdalon, Ephedra, Lycium and Various Composits; 

 others have evidently worked their way along the margin of the plateau and 

 thence up the canyons as they have excavated their way back into the in- 

 terior; of this class probably are the Junipers, Hackbcrry, Shin Oak and 

 Soapberry or AYild China; still others, like the Willows and Cottonwoods, 

 may have been introduced from the northwest through the Canadian River 

 valley. The Honey Locust, Bittersweet vine and some of the hcrl 

 species present special problems of peculiar interest as to their origin and 

 method of introduction. In the case of Gleditsia iriacanthos the rather 

 heavy seeds must have been transported from sections far to the east or 

 southeast, the lower Brazos valley or the valley of Red River in eastern 

 Texas and Oklahoma being the nearest sections where it occurs, so far as 

 I an\ aware. 



One of the best internal evidences of a newly established or changing 

 flora is the lack of completeness and general balance in its composition and 

 organization as compared with that of the zone it occupies and similar ad- 

 jacent regions from which its plant population must have been drawn. In 

 a plant society long established this adjustment has been brought about by 

 ages of keen competition and elimination, compelling each surviving mem- 

 ber to make the most of every opening and every available space; while in a 

 newly invaded region not only is there evidence of the somewhat confused 

 mingling of the old and new elements but the recent emigrants are arranged 

 in a more or less haphazard way and are apparently seeking their true posi- 

 tion or experimenting on the possibility of finding a permanent place in the 

 flora. This partial lack of symmetry and order in the plant society may, if 

 the geological history and physiographic development of the region as well 

 as of the ever changing boundaries of the flora are not kept clearly in mind, 

 be as little explicable under the modern theory of plant succession as under 

 the old discarded idea of special creation, by which each species was sup- 

 posed to have been placed for definite useful purposes in the particular en- 

 vironment for which it was best fitted: for plants perfectly adapted to a 

 region that has undergone profound climatic or nhv.siofTmnriiV rlmnnrAs rin 



