34 Richard H. Boerker 
Species that seemed to be affected most were those from the 
Black Hills and New Mexico and those affected least were those 
from the Pacific coast. Intermediate between these were those 
species obtained from Montana and Idaho. The coast species 
affected most was Sequoia washingtoniana. Pseudotsuga taxi- 
folia was much less affected than Pinus ponderosa taking into ac- 
count all the varieties of each. 
The conditions and cultures which were favorable to damping- - 
off are of interest in that they emphasize many points already 
known about this part of the subject. Loam is more dangerous 
than sand or gravel due to its moisture retentiveness. The shade 
cultures were more affected than the open light due to a greater 
soil moisture content in the upper layers of soil. The moist cul- 
tures were affected more than the dry ones and the shallow soil 
cultures more than the deep soil ones due to a greater amount 
of soil water per unit of volume of soil. Humous soils, soils with 
decaying vegetable matter, and manure soils should be avoided 
because they contain myriads of fungus spores. The data for 
Pinus divaricata is given as representative of the three worst 
affected species. The per cents. given below are those of the 
number of plants killed (out of the total number that germinated ) 
within five weeks after planting the seed. Two hundred seeds 
were planted in each culture: 
Pinus divaricata KILLED By DAMPING-OFF 
Light Cultures | Soil Moisture Soil Depth | Soil Texture 
Opente ee Spl IDiay Stolle g oo66 6 ONDE ooo o105 ab 8% ‘Loam Vie cca cers 35% 
Medium..... 26% Medium soil. ..24%|Medium....... ASGs| Sail, oo basco 56 1% 
Densekumeas: 90%|Wet soil....... 25 7o\Shallowesseee OnGAGranalacocoacs o% 
THE EFFECT OF HABITAT FACTORS UPON GERMINATION 
This problem was undertaken because it was felt to be of funda- 
mental significance not only to silviculture but to ecology as well. 
Not only was it desired to throw more light upon some of the 
phases of this problem that had already been partly worked out 
and to modify, if necessary, some conclusions that have been 
drawn, but it was my intention to throw some light upon phases 
