164 Forestry Quarterly 



Each of these three exposures for each of the three diflferent 

 days (sunny, cloudy and windy) consisted of seven lots of 100 

 trees each, respectively exposed 10 minutes ; 20 minutes ; 40 min- 

 utes ; 1 hour ; 2 hours ; 3 hours ; and 4 hours. The total number 

 of trees exposed will be seen to be (3 x 3 x 700) 6,300, besides the 

 row of 25 unexposed check trees for each 100 (4 rows) exposed 

 trees, or a total of 1,575 check trees, making a total of 7,875 trees 

 in the whole experiment. The check trees were placed syste- 

 matically and made up each fourth row, so that any localized 

 influences might be detected. This was very wise, for it enabled 

 Mr. Harbeson to immediately detect the advent locally of Lopho- 

 dermium pinastri — and to accurately reject the few lots thus 

 attacked. 



The planting stock used was a very strong two-year seedling 

 taken up and tied loosely in bundles of 50 and heeled in with no 

 appreciable exposure to await the sunny, cloudy, and windy 

 days determined upon for exposure. 



When the bundles were taken up for exposure, the roots were 

 spread out on the sloping side of a compost heap so that the 

 sun's rays would strike them about perpendicularly. They were 

 turned carefully so that the drying out might be as uniform as 

 possible. 



After the fall exposure the bundles were carefully tagged, as 

 were the unexposed check bundles, and heeled in in trenches in a 

 well sodded site with good drainage and a northwest slope. The 

 exposures were stopped on the minute and the seedlings puddled 

 and heeled in. 



Series I. — Exposure on a Calm Sunny Day. — The fall expo- 

 sures were made during the afternoon of November 22, 1913. It 

 was an ideal calm sunny day, temperature 72° to 57° F. The 

 four-hour exposure ran from 1.30 to 5.30 p. m. 



The spring exposures were made on April G, 1914, clear and 

 sunny with a perceptible air movement from the northwest. Tem- 

 perature 30° to 55° F. Wet bulb 40°, dry bulb 48° at 12.30 a. m. 

 indicating a relative humidity of 48 per cent. At 5 p. m. the tem- 

 perature rose to 55°, and the relative humidity consequently fell 

 to 39 per cent. 



Series II. Exposure on a Calm Cloudy Day. — The fall ex- 

 posures were made on the afternoon of November 8, 1913, the 



