132 BOTANICAL GAZETTE [AUGUST 
and often take on xerophilous characters. In the following account 
these zones are spoken of as the central zone and the mafle-alder zone 
respectively. The bog water and bog soil used in the experiments 
were brought every month to the laboratory in glazed earthen-ware 
jugs from stations which remained identical throughout the period 
of investigation. 
To ascertain the osmotic pressure of the bog water, determinations 
of the freezing-point were made. As compared with the freezing- 
point of pure distilled water the average lowering in the various deter- 
minations is 0°007 and 0°0og for the central station and the maple- 
alder station respectively. Compared with similar determinations 
for Michigan bogs (13) the bog water of Buckeye Lake has no higher 
concentration. 
Data on temperature deviations in the bog substratum are omitted 
here as having no particular significance in the problem at hand in 
this region. They do not seem adequate to account for the differences, 
since plants growing in soil, nutrient solutions, or bog water are equally 
affected. If there is any property of bog water which prevents rapid 
and successful invasion of plants, this inhibiting influence must rest 
not in the physical character of the habitat alone, but in some chem!- 
cal quality as well. 
A study of the acidity of the bog water under examination gave 
results differing but little from those obtained in the Michigan bogs 
(13). Titrations were made with a n/1oo KOH solution. The 
bog water from both zones is alkaline to methyl orange and acid to 
phenolphthalein. A comparison of the acidity figures shows that the 
bog water of the central station is uniformly less acid than that of the 
maple-alder zone. Boiling, however, greatly reduces the acidity ° 
the bog water in the latter station. This is due to the escape of car- 
bonic acid. In the light of the results here brought out, the presence 
of the toxic bodies is not necessarily to be correlated with high acidity : 
To determine the presence and possible nature of the injurious 
substances affecting plants through their toxic effects, the following 
experiments were planned. Familiarity with the behavior and the 
conditions of development of Marchantia polymorpha (4) suggest 
marchantia gemmae of known history as an indicator for preliminary 
observations. A large number of gemmae were placed in cryst 
