COMPARISON OF SEED TESTING 693 



give better drainage. The depth of the sowing surface, as well as its 

 uniformity, was regulated by pressing a board of uniform thickness 

 into the tray until another board nailed crosswise came to rest on the 

 upper edges of the tray. An even depth of cover for the seed was 

 secured by a straight-edge notched at the ends, so that the lower part 

 fitted into the box, while the ends rested on the rim of the sand tray. 

 The depth of cover was regulated by the distance the lower part ex- 

 tended below the rim of the tray. The difference between the thickness 

 of the board used to form the sowing surface and the distance the 

 straight-edge extends into the box is the depth of cover. 



The seeds of larix, picea, thuja, pseudotsuga, and pinus contorta were 

 covered one-half inch deep and the remaining species three-eighths 

 inch. Watering was done with a hand sprinkler and in small quanti- 

 ties, so as to avoid any shifting of the sand cover. The water was ap- 

 plied only after the upper part of the sand began to show signs of 

 drying. 



Chemical agents were not used for sterilizing either the germinator 

 or the sand tests, for it has been found that this is injurious in both. 

 Sufficiently sterile sand is obtained at a depth of 6 feet below the ground 

 surface and the water is fairly free from spores. In the germinator 

 the seed was washed under cold, running water every three days to 

 remove fungus spores, and at the same time the mats under the seeds 

 were changed and sterilized by boiling and new sterile filter papers 

 supplied. 



Both the sand and the germinator tests were carried on during the 

 winter months in the greenhouse, where heat was supplied by hot-w^ater 

 pipes. The temperature of the sand had a diurnal fluctuation between 

 60 and 90 degrees Fahrenheit, occasionally reaching 55 and 95 degrees, 

 while that in the germinator ranged between 65 and 87 degrees Fahren- 

 heit. 



The results of these comparative tests are shown in the following 



tables : 



Table i. — Average Germination per Cent 



Tests in Jacob- Tests in Davs 



Species. sen firerminator. sand. 



Larix occidentalis 60.3 28.5 26 



Pseudotsuga taxifolia ' 49-0 39-2 26 



Pinus ponderosa 36.7 i5-5 30 



Pinus .monticola 22.0 18.5 32 



Pinus strobus 12.0 6.5 3S 



Pinus contorta 60.7 58.3 21 



Thuja plicata ^^-i 54-7 24 



Picea engelmanni 79-2 37 -7 '5 



Tsuga hetcrophylla 40. 7 40.5 24 



