6 BULLETIN 1263, L\ S. DEPAETMEXT OF AGRICULTURE 



On June 30, 1922, enough seed 4 of lodgepole pine, Engelmann 

 spruce. Douglas fir, and western yellow pine was sown in four of 

 the seed-testing tills, to secure approximately 100 seedlings of each 

 species in each till. The contents of one till were used for each pe- 

 riodic test. The soil was coarse and derived by sifting from the 

 granitic soil of the region. In order to secure the best germination 

 the tills were kept under the regular seed-testing conditions, which 

 include a daily maximum temperature of about 85° F. at the soil 

 surface. They were watered daily. Germination was prompt, all 

 species starting in from 7 to 15 days, and all seeds but those of lodge- 

 pole pine germinated fully within about 30 days. 



The first test was made July 30, when the seedlings were heated 

 in the electric oven, the temperature of which is readily regulated 

 and controlled by a thermostat. The atmosphere within was kept 

 saturated by means of a pan of water placed over the heating coil, 

 the object being to reduce the drying of the seedlings to the lowest 

 possible point. The procedure was as follows : 



For each subtest, five seedlings of each species, selected at ran- 

 dom, were so placed between wet blotters that the root portion of 

 each was protected and well supplied with water, while the aerial 

 portion was exposed. The blotters were held together with clips, 

 and the whole was placed in the oven in a horizontal position, with 

 the leaves of the seedlings not in contact with any solid object. A 

 maximum-registering thermometer was placed with its bulb in the 

 same plane with the leaves of the seedlings. At the expiration of 

 the allotted time, the packet was promptly removed from the oven, 

 the thermometer was read, the time noted, and the blotters again 

 moistened and placed so that the seedlings projected over the edge of 

 a table. As the seedlings wilted, they were removed and the time 

 at which wilting took place was noted. After the immediate obser- 

 vation each set was removed to the side, kept moist, and observations 

 made for wilting at intervals of a few minutes for seven hours. 



For the three later tests, made on August 15, September 2, and 

 September 28 and 30, an entirely different plan was followed. The 

 purpose was to produce a heating and drying effect similar to that 

 produced by sunlight. A commercial electric heater was used as the 

 source of heat. The heating coil, which uses about 550 amperes, is 

 2 J inches long, and 1£ inches in diameter, and the reflector 8} inches 

 in diameter. 



For the second test the seedlings from one of the tills were trans- 

 planted about August 5, after being hardened by continuous ex- 

 posure to the sun for several days. Ten deep 6-inch galvanized pots 

 were prepared, each containing six seedlings of each species placed in 

 rows. These pots were exposed to the sun five days prior to the 

 time of the test and given water each day until the day before the 

 test. The soil was decidedly moist at the time of testing. 



One pot was used for each subtest. To attain various temperature 

 effects, the electric coil was placed at distances varying from 1 to 2.5 

 feet from the center of the top of the pots at angles of 45° to 75° with 

 the surface of the soil. Two thermometers wore used, one with the 



* Tlio source and quality of the seed employed is :i matter of record, and for present 

 purposes need nol be described. 



