84 .1. Daohnowshi — Problem of Xerornorjphy, 



in the fact that the present vegetation of undrained swamps 

 and of bogs has many of these xerophytic features, none of 

 which arc correlated with atmospheric influences. The chief 

 cause for both the xerophily of the coal flora and the great 

 accumulation of vegetable matter is not to be looked for merely 

 in climatic implications. High temperature and humid air 

 do not promote, in a high degree, decomposition. The for- 

 mation of peat has been reported even for regions about the 

 equator.* The great thickness of the Carboniferous deposits 

 suggests, however, that the preservation of the debris was 

 favored by a temperate climate and by agents in the soil such 

 as are involved in the accumulation of peat to-day. Simi- 

 larly the force of the inference from the xerophytic aspect 

 of the Carboniferous vegetation, — namely, the peculiarities of 

 leaf size and leaf structure for maintaining a balance between 

 supply and loss of water, — gives additional support to the 

 view that the plants encountered adversities of' soil-water 

 content rather than of climate. A satisfactory explanation of 

 the phenomenon, not controverted by any known facts, has 

 been found in the experimental investigations of the writer on 

 the reduction action and toxic character of bog water and bog 

 soil,f the results of which are briefly as follows. Poorly 

 drained and undrained water basins and lowlands, whether in 

 areas characterized by limestone formations, by sandstone, or 

 glacial drift, become physiologically arid habitats with the 

 accumulation of vegetable debris. Although water is so 

 abundant in bogs and swamps, yet it is largely unavailable to 

 the plants on account of various decomposition products due to 

 the activity of low organisms in the debris-substratum, espec- 

 ially such saprophytes as bacteria and fungi. Peat soils con- 

 tain bacteria and other fungi in greater number than supposed 

 hitherto, inducing diastatic, inverting, proteolytic, cytohydro- 

 lytic and reducing action in the upper layer of the substratum. 

 They vary in kind and number with the nature of the sub- 

 stratum, and show marked interdependence as well as antagon- 

 istic action. It has been found that, as a general rule, there is 

 an accumulation of injurious substances which must be removed 

 if no deleterious action is to follow, and if complete decompo- 

 sition of the debris is not to be retarded. The complex and 

 rather ill-defined, " humus acids," more specifically humic, 

 ulmic, crenic and apocrenic acids, are not the important con- 

 stituents to which peat owes its antiseptic properties and which 

 interfere with the action of bacterial organisms. In Ohio peat 

 deposits, at least, the presence of injurious substances in the 



* Potonie, H.. Die Entstehung der Steinkohle, 152. Berlin, 1910. 

 f Dachnowski, A. The Vegetation of Cranberry Island and its relations to 

 the substratum, temperature, and evaporation. Bot. Gaz., li, 1911. 



