April, 1911.] 
The Ancient Vegetation of Ohio. 
3 2 5 
which are briefly as follows: Poorly drained and undrained 
water basins and lowlands whether in areas characterized by lime- 
stone formations, by sandstone, or glacial drift, become physio- 
logically 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 decom- 
position products due to the activity of low organisms in the 
debris-substratum, especially such saprophytes as bacteria and 
fungi. Peat soils contain bacteria and other fungi in greater 
number than supposed hitherto, inducing diastatic, inverting, 
proteolytic, cytohydrolytic and reducing action in the upper 
layer of the substratum. They vary in kind and number with 
the nature of the substratum, and show marked interdependence 
as well as antagonistic action. It has been found that as a gen- 
eral rule there is an accumulation of injurious substances which 
must be removed if no deleterious action is to follow, and if com- 
plete decomposition 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 constituents to which peat owes its antiseptic 
properties and which interfere with the action of bacterial organ- 
isms. In Ohio peat deposits, at least, the presence of injurious 
substances in the substratum is not in direct relation to acidity 
in the soil. Tests on the reducing powers of peat soils show that 
the wind driven aeration has little effect on the peat substratum 
beneath the two-feet level. A shallow superficial zone of oxida- 
tion exists in peat soils, and the debris below this is sometimes so 
charged with injurious decomposition products and gases, and so 
far unaerated as to be inhospitable to all organisms but anaerobic 
bacteria. 
In the growing season the temperature of peat soil in the 
more xerophytic of the succeeding bog associations is not below 
that of other soils. Rapid and passing changes of air tem- 
peratures and the occasional extremes do not affect the sub- 
stratum temperatures. Only average effects prevail and the 
great periodic changes of the dominant climate. The tempera- 
tures of the deeper peat strata indicate that there is scarcely 
anything of a seasonal descent analogous to the circulation or 
“overturn” in lakes or in ocean. 
The continued growth and persistence of the closely related 
plant association and the slow succession of vegetation types in a 
habitat of that character is no longer incomprehensible if we 
remember that the vegetation grows on top of the accumulating 
debris and that the water table is always at a high level. The 
disturbance of the balance produced in the soil is thus not unfavor- 
able to the dominance of the associations. There occur natural 
successions which are determined, however, not by a deficiency of 
