250 



MISSOURI BOTANICAL GARDEN. 





Distribution and Phenology 



Aspleniuin tlielyptcroidee 1 



Cheilanthes lanuginosa 2 



Comptosoriis rhizophyllus 3 



Cystopteris bulbifera 4 



Cystopteris f ragilis 5 



Onoclea sensibilis G 



Pellaea atropnrpurea 7 



Phegopteris hexagonoptera 8 



Pteris aqnilina 9 



Woodnia obtusa 10 



Botrychium virginiantim 11 



Ophioglossuni Engelnianni 12 



leoetes melanopoda 13 



Azolla caroliniana 14 



1 



Weeds 



2 



3 



4 





5 



6 7 

 I 



± 



*t 



=b 



MIS- 



Upland 



8 



± 



9 I 10 11 12 13 14 



± 



+ 



± 



± 

 ± 

 ± 

 4- 





SUMMARY. 



The area covered is too small to attach importance to a 

 variation in climatic factors, i. e., seasonal means and ex- 

 tremes of temperature, the amount and distribution of rain- 

 fall, the humidity of the air and the movements of the 

 atmosphere, factors which determine the type of the vegeta- 

 tion and the type of the flora,* as influencing the distri- 

 bution of the different local species through the various 

 regions which may be distinguished in the section studied. 

 Where most conditions are fairly uniform, as for instance on 

 the western plains or the plateaus of the Yellowstone, the 



presence of any plant, and modifications of its habit, its 

 morphological, phenological and oven minute physiological 

 characters, may frequently be ascribed to modifications of a 

 single factor. The physical condition, including color, of the 

 soil, and the amount of water present and available, the 

 presence or absence of a single element, variation in the 

 amount of another, differences in the amount or nature of 

 light, the direction and intensity of the prevailing winds, 

 altitude and a number of other factors, yield instances too 

 well known to require repetition here. But where conditions 



are diversified the agency of a single factor is no longer a 



* Schimper, A. F. W. Pflanzengeographie. 174, 1898 



