A. Dachnowski — Problem of Xeromorphy. 33 



Art. IV. — The Problem of Xeromorphy in the Vegetation 

 of the Carboniferous Period ; by Alfred Dachnowski. 



The comparatively abundant information which we possess 

 concerning the present vegetation in aspect, form, structure 

 and function as related to differences in physical, chemical and 

 biological factors, is in striking contrast to the absence of a 

 correlation of similar data as regards environmental conditions 

 during geological periods. From the point of view of ecology, 

 the vegetation conditions of the past are of considerable value, 

 however the method of endeavor to understand the factors 

 which the fossil plants record. Those who have confined their 

 ecological study to the environmental investigations of the 

 present must sooner or later test and supplement their investi- 

 gations by reference to the past, correlate structural character- 

 istics with physiological conditions of growth and apply the 

 knowledge of relations gained from living plants. Whether or 

 not the data can be accepted as sound links in the chain of evi- 

 dence rests largely in the value of the experimental work at 

 hand and in the degree with which they interpret many 

 apparent anomalies. 



The limiting climatic and physiographic features which 

 characterize bogs, and the structural features and functions of 

 the vegetation peculiar to them, have seemed to the writer of 

 sufficient interest to invite attention to an inquiry on the prob- 

 able cause of the xerophily of many of the Carboniferous 

 plants which lived in swampy areas. The present paper is 

 intended, therefore, as a continuation of the ecological studies, 

 which appeared from time to time on the vegetation of an 

 Ohio bog and peat deposits. The problems involved in the 

 following discussion are by no means to be solved within the 

 limits of this paper ; merely an adjustment of perspective is 

 made, leading from a consideration of the fossiliferous plant 

 remains of the Coal Measures. 



The characteristic xerophily of the Carboniferous vegetation 

 has been interpreted by geologists as indicative of a warmer, 

 moister atmosphere, more heavily charged with carbon dioxide 

 than at present.* To the writer the facts are hardly consistent 

 with the external conditions assumed. The supposition that 

 xeromorphy involves factors of climate is not necessarily 

 wrong, but calls for a fuller consideration and comparison 

 along with additional factors, the character and magnitude of 

 which is capable of producing like results. A more satisfactory 

 interpretation of the phenomenon of xerophily would be found 



* Chamberlin, T. C, and Salisbury, E. D., Geology, ii, 603, New York, 

 1906. 



Am. Jour. Sci.— Fourth Series, Vol. XXXII, No. 187.— July, 1911. 

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