PROPAGATION BY MEANS OF SEEDS AND SPORES 31 



Testing for purity 



Analyzing a sample of seed for the impurities it may con- 

 tain is a subject quite foreign to a manual of propagation ; yet 

 the reader may desire a few words on the subject. The process 

 consists in examining the sample under a lens and counting or 

 estimating the proportion of impurity or mixture. To make 

 the best and most convincing test, one should be able to identify 

 the impurities. Following is a description of such analysis 



FIG. 19. Instruments for seed examination. The seed sample ; lens ; piece 

 of cardboard or other material to separate the sample into piles or parts ; for- 

 ceps ; scalpel or knife. 



for home use from Girc. 23, Utah Experiment Station (1916), 

 by George Stewart, together with a picture (Fig. 19) adapted 

 from the Montana Experiment Station : 



"To find out the quality of the seed that is commonly planted, testing 

 for impurities and germination power is the first important step. Let all 

 seed be run over screens to get rid of as much foreign substance as pos- 

 sible. After a thorough screening, an analysis should be made. The 

 most practical method for ordinary purposes is the hand separation of a 

 well-mixed sample into piles containing (1) good seed; (2) broken and 

 injured seed of the same kind ; (3) seed of useful plants or of other varie- 

 ties of the same crop; (4) dirt, chaff and other inert material; and (5) 

 weed seed. 



