SEED TESTING 119 



For determining the weight by volume one and one-half quarts 

 are usually required. It goes without saying that the samples from 

 each lot must be chosen with the utmost care. First, the shipment 

 must be thoroughly mixed, then at least ten samples, selected from 

 different places in the pile, are mixed and a final average lot selected. 

 When the seed comes in sacks 5 samples can be extracted from each 

 sack or from a certain proportion mixed together and sampled as given 

 above. Where samples must be sent away for testing they must be 

 labeled and sealed in air-tight bags, but if the water content of the 

 sample is to be determined the shipment is made preferably in corked 

 glass or air-tight metal boxes. It is of value to keep samples of seed 

 known to be normal to use as a basis for comparson; with reliable samples 

 officers that are not experts can readily check species and, occasionally, 

 varieties. The separation of the debris from the real seed can best be 

 made by hand. The seeds are placed on a glass and separated from the 

 wings, particles of cone, refuse, debris, wood, sand, and damaged or 

 puny seed by the use of a penknife. The operation must be completed 

 as soon as possible to guard against changes in weight due to drying. 

 The absolute weight is determined by averaging the weight of two 

 lots of 1,000 seeds each; with this figure the number of seeds to the pound 

 can be decided by multiplication. When the amount of seed per quart 

 is to be secured a number of quarts must be averaged owing to the 

 variations usually encountered. 



A reliable germination test must include four separate lots of 100 

 seeds each, or for acorns and nuts four of 50 seeds each; the choice of 

 which seeds to use must be by lot to eliminate absolutely the personal 

 element. After the tests on each lot the results ought not to vary more 

 than 10 per cent for seed with high germination powers nor more than 

 15 per cent for seed germinating around 50 per cent. Before the germi- 

 nation tests it is customary to soak conifer seeds in sterilized luke- 

 warm water for from 6 to 15 hours. This time counts on the total length 

 of time allowed for germination. For germination Fron recommends 

 a heavy sterilized blotting paper or sand with a Schribaux stove, the 

 humidity being kept at 50 per cent to 60 per cent during the entire test. 

 No chemicals are used. The temperature is maintained between 

 20 C. (68 F.) and 30 C. (86 F.); for conifers Fron recommends a 

 temperature of 20 C. to 25 C. (68 F. to 77 F.) during 18 hours, and 

 25 C. to 30 C. (77 F. to 86 F.) during 6 hours, but Schwappach 

 recommends 25 C. and 30 C. (68 F. to 86 F.), respectively. Mari- 

 time pine can stand up to 35 C. (95 F.) for short intervals. Ordinarily 

 no light is admitted, but alder and birch appear to germinate more 



5 In Germany the sampler (Sonde) of Professor Noble, made by Mathes, of Tharandt, 

 Saxony, has been used with success. 



