154 BOTANICAL GAZETTE [AUGUST 
The roots of all species were thicker and thriftier looking on the 
raw humus than on the mild humus, although fir and white pine 
were a little more branched on the mild humus. Most striking of 
all, the roots of all 3 species on the raw humus were still capable of 
absorption, even at the end of October. This was shown by the 
presence of a considerable number of the little translucent growing 
tips which are found during the height of the growing season. On 
the mild humus growing tips capable of absorption were almost 
lacking except where the root came in contact with the wood of 
the flat. In the raw humus the root tips which had ceased to 
function became brown, while many of those on the mild humus 
became covered with a white fungus. A black fungus, common in 
the raw humus of the forest, was found attacking the roots on the 
mineral soil more than those on the raw humus, indicating that its 
presence may be due to low vigor on the part of the roots rather 
than to abundance of spores. The rootlets in the raw humus 
exhibited a propensity for searching out twigs and cones and 
growing through them. - 
- Raw humus appears to have an effect on damping off fungus, 
_ quite the reverse of what might be expected. In an experiment to 
determine the effect of drying out, such as the raw humus is sub- 
| jected to under natural conditions in the open, upon the germina- 
tion and establishment of Pinus resinosa, it was found that on raw 
a humus kept artificially moist there was no damping off, while on 
the raw humus which received no water except from rain the loss _ 
a from damping off was 44. ‘ ner cent of the seedlings germinating. 
yrse on a dry than on a moist 
: cn soil i is contrary to all previous gene The explanation is 
_ probably y to hag found it in the great abundance of fungus spores in 
y nursery soils, and in the LS 
