374 



BOTANICAL GAZETTE 



[NOVEMBER 



The following table shows some other physical properties of these 

 several varieties of peat. 



*Low volume percentage due to air present in tissues. 



These measurements were made by placing the peat samples in a 

 zinc cylinder of 600 cc capacity. The bottom of the cylinder was 

 closed with a wire gauze cap. The moist peat was tamped into the 

 cylinders with as nearly uniform a stroke as possible. The cylinders 

 were then set in a dish of water for eighteen hours, after which the 

 cylinder was removed and allowed to drip. When all dripping had 

 ceased, the cylinder was weighed. The peat was then removed and 

 allowed to dry at room temperature, and again weighed. Finally it 

 was dried at 110 C., and the absolute weight determined. As usual 

 in such measurements, considerable irregularity was shown by the 

 different samples, owing to the difficulty of removing the air, and of 

 packing to the same degree. However, the figures bring out clearly 

 the fact that sphagnum more than any other plant influences the 

 water-capacity of a peat containing it. The eriophorum peat has a 

 lower capacity, owing to its coarse fibrous structure. Of the series 

 examined, the highest water-capacity was found in the cassandra 

 zone. The effect of further decay and destruction of the plant tissue 

 is shown by the reduction in water-capacity of the last three members 

 of the series. The percentages are of interest in connection with the 

 utilization of such lands for agricultural purposes, in showing the 

 difficulty of proper drainage. It is the experience of the men who 

 ditch these bogs that until the peat has reached the condition termed 

 "muck" the ditches act only with extreme slowness. 



Chemically, peat or humus is made up of varying quantities of 

 several substances of a rather indefinite character, which are com- 

 monly classified among the dehydration products of the carbo- 



