Results of Seed Tests, 1929 3 



again once a day for the wliole period. Uniform moisture 

 must be provided also, not alone by an absorbent substra- 

 tum like cloth or blotting paper placed in a saturated at- 

 mosphere but by means of capillary wicks suspended in 

 an adjacent free water surface. Canada bluegrass requires 

 a glass germinator for controlling temperature and mois- 

 ture in order that it may be flooded with light, either nat- 

 ural or artificial, for a certain period of each day. Some 

 seeds require, for best results, absorbent cotton for a sub- 

 stratum rather than blotting paper or cloth. Ordinary let- 

 tuce represents such a species. Certain kinds respond bet- 

 ter when the substratum is wet with a very weak solution 

 of potassium nitrate, but in nearly all cases pure water on- 

 ly is used for moisture. Ordinary blotting paper, even 

 when pure white, is often fatal to well known species like 

 timothy because of alum or other soluble salts commonly 

 employed in its manufacture. To guard against this dif- 

 ficulty, only the most carefully prepared blotting paper, 

 especially manufactured for the purpose, is used. Ours is 

 obtained from a large manufacturer in Washington, D. C. 

 Purity tests require a corresponding amount of care and 

 attention to detail. Careful sampling in the store, and 

 correct division of the sample in the laboratory are impor- 

 tant preliminaries to accuracy in this phase of the work. 

 For each of these purposes, special instruments and ma- 

 chines are provided. It is not enough to be able to tell 

 l^ure seed from adulterants, difficult enough in many cases, 

 but the analyst must also distinguish between the imper- 

 fect glumes of such seeds as oats, redtop, bluegrass and 

 similar species, and the glumes which inclose a perfect seed 

 of potential germinative capacity. These species which 

 ordinarily carry chaffy glumes covering the seed proper, 

 as threshed from the straw and as best protected against 

 molds and other diseases for planting purposes, often pro- 

 vide apparently healthy seeds which reveal nothing but 

 empty glumes on careful examination. This distinction 



