32 Richard H. Boerker 
Soil temperature was not measured. With the air temperature 
at an optimum point during the entire experiment it is reasonable 
to assume that the soil temperatures were likewise always at an 
optimum, at least they were never at such a low,nor at such a 
high point so as to affect materially the germination of the seeds 
or the growth of the seedlings. 
Notes on Damping-O ff . 
No special investigations were conducted to determine what 
species were most affected and what conditions of light, moisture, 
and soil were most favorable for the development of this group 
of fungous diseases. This part of nursery practice is a problem 
of no small importance in itself and the only data here given is 
that which had to be taken in connection with this series of in- 
vestigations. Therefore these are merely notes and suggestions, 
which, while conclusive as far as they go, must be substantiated 
in the future to be of any permanent value. 
It was found that the pines were most affected. Pinus divari- 
cata at the end of five weeks was affected most. About 15 sepa- 
rate cultures of 200 seeds each of this species were started and 
most of these showed more or less serious effects of the disease. 
Several cultures of Pinus resinosa failed after six weeks. Pinus 
palustris damps off in loam before it really gets its crown above 
ground. In this case the loss was reduced in the sand and gravel 
cultures. Both the New Mexico and South Dakota varieties of 
Pinus ponderosa after five weeks damped off considerably, leaving 
only from 10-25 per cent. of the original stand. The following 
is a list of species in the order in which they were affected in 
loam under normal conditions of light and water. The first men- 
tioned were affected most: 
Pinus divaricata Pinus ponderosa (N. M.) 
Pinus resinosa " Robinia pseudacacia 
Pinus palustris Pinus strobus 
Pinus ponderosa (S.D.) Pinus taeda 
It appears that the seeds of trees of certain habitats when 
germinated in soils or under conditions different from those ob- 
taining in their natural environment are affected worst. These 
habitats are: 
