TESTING SEEDS AT HOME. 179 



Moisture is as important as temperature, liei'ore a seed can sproiM 

 it must absorb water and swell. Though the swelling of a seed is a 

 necessary preliminary, it is not always followed by germination, for 

 the absorption of water is a purely mechanical process and does riot 

 imply vitality in the seed. The entrance of water into the seed is 

 dependent upon the structure of the seed coats. When these are 

 hard and impervious, as is often the case in leguminous seeds and in 

 nuts, water gains admission slowly and germination is retarded. In 

 cereals and in most garden seeds the seed coats are easily penetrated 

 by water, the seeds swell rapidly, and germination is prompt. Experi- 

 ments have proved that seeds will absorb moisture and swell in a 

 damp atmosphere, but that Tor germination, contact with water is 

 necessary. An atmosphere saturated with water vapor is not suffi- 

 cient to induce germination. Flaxseed kept in a saturated atmos- 

 phere for nine days, and. seed of kohl-rabi kept under the same 

 conditions for twenty-two days, did not germinate (Nobbe, Ilaiidbuch 

 der Samenkuiide). Too much water is equally injurious. As a gen- 

 eral rule, seeds will not germinate well when immersed in water. 

 It is necessary to have the seeds in contact with some medium from 

 which they can obtain an abundant supply without allowing water 

 to stand around them. 



Light exerts a harmful influence upon germination. Experiments 

 have shown that seeds placed under colored glass did not germinate 

 as rapidly as those which were in complete darkness. Even more 

 important than the exclusion of light is the free access of air and 

 the escape of the noxious gases generated by germinating seeds. 

 When germination has commenced, carbonic acid gas is given off, 

 which must be allowed to escape, or growth will be checked. 



SELECTING SAMPLES. 



Selecting the sample to be tested is a matter of great importance. 

 It must be a fair sample, including both good and bad seeds. If the 

 quantity to be tested is considerable, small amounts should be taken 

 from different parts of the mass. These small samples, thoroughly 

 mixed, form the larger sample out of which the proper number of 

 seeds is to be counted. In case the quantity of seed is small, say 

 one-half pound of clover seed, pour the seed from the package into 

 a pan, taking a small spoonful occasionally from the stream. From 

 the quantity thus secured a sample for testing is taken. The number 

 of seeds used in testing depends upon the size of the seed and upon 

 I he quantity at disposal. 



If the sample is large enough, 100 seeds of the larger kinds and 200 

 to 400 of the smaller seeds are taken. The increased number is a 

 check upon error in counting small seeds. In counting out the seeds 

 a fair number of small and immature ones should be selected as well 

 as the large and plump ones. There is reason to suspect that in some 



