Problems of Physiological Plant Ecology. 41 



Mexico are more of the nature of dark compact layers of humus, 

 rather than of peat. Such high mountain deposits fill shallow 

 depressions between rock masses and are rarely over several 

 inches in thickness. The material is extremely friable, but of a 

 dark brown color, resembling bog peat in all of its essential 

 characters. Such mountain peat is rarely due entirely to 

 Sphagnum, but represents the accumulation of the remains of a 

 considerable number of mountain species. For example, on 

 Roan Mountain, the sand myrtle (Dendrium buxifolium) and 

 Carolina rose bay (Rhododendron catawbiense) grow out of such 

 peaty soil, which is constituted of their remains and those of 

 mosses. The most extensive and interesting peat deposit was 

 found on Mt. Mansfield along the western side of the saddle 

 that connects the Chin with the higher part of the mountain. 

 There the peaty deposit formed by sphagnum and other plants 

 was about half an acre in extent and at least two feet in thick- 

 ness. Throughout this peat were found the bleached but 

 perfectly preserved roots of the balsam (Abies balsamea), remains 

 of the Labrador tea (Ledum groenlandicum) , the black crow- 

 berry (Empetrum nigrum) and other plants found on this 

 mountain peak. 



(Concluded in March number.) 



PRESENT PROBLEMS OF PHYSIOLOGICAL PLANT 



ECOLOGY.* 

 By Burton Edward Livingston. 

 By physiological ecology is here meant merely the study of 

 the factors which determine the occurrence and behavior of 

 plants growing under uncontrolled conditions. Field physiology 

 would almost be a synonym for the term here used. While 

 pure physiology proceeds, as far as is possible, with controlled 

 conditions, ecology must perforce proceed without known con- 

 ditions, without the synthetically built up environment of pure 

 physiological research. H^re it is necessary to measure and 

 analyze natural conditions and to relate these to the behavior 

 of the plants. The problem of measuring the plant phenomena, 

 the determination of the number, size, form, structure, etc., of 



* The paper from which this article is abstracted was presented in the Ecological 

 Symposium of The Botanical Society of America at the Baltimore meeting, December 30, 

 1908. 



