74 SEEDS AND FRUITS 



FEB CENT OF GERMINATION FOR EACH OF 6 YEARS 

 OF STORAGE 



Purity and the Analysis of Seeds 



The impurities of seeds consist of seeds of other species and of 

 dirt, such as soil particles, chaff, hulls, and other plant fragments. 

 In sowing impure seeds one can not estimate the amount of 

 desirable seeds sown unless the percentage of impurities is pre- 

 viously determined so that allowance can be made. Besides one 

 is likely to sow the seeds of undesirable plants, which choke the 

 crop and cause much trouble and expense in eradicating them. 

 A small per cent of weed seeds is often a serious matter. For 

 example, in sowing Grass seeds which contain only 1 per cent of 

 weed seeds there is the possibiUty of 20 or more weeds to the 

 square yard. Nobbe found enough weed seeds in a certain 

 sample of Timothy seeds, if sown at the ordinary rate, to supply 

 24 weeds to every square foot of land. Furthermore, in purchas- 

 ing impure seeds, unless a deduction from the price is made for 

 the impurities, one pays more than he should for the desirable 

 seeds obtained. 



More impurities occur among the smaller agricultural seeds, 

 as Grass, Clover, and Alfalfa seeds, than among the grains, al- 

 though a few very bad weed seeds, such as those of Quack Grass 

 {Agropyron re-pens), Cow Cockle {Saponaria Vaccaria), Corn 

 Cockle (Lychnis Githago), and Enghsh Charlock {Brassica 

 Sinapistrum) , are common among the small grains. 



Seed Analysis. — A bag of seeds may be analyzed for two 

 reasons: (1) to determine the percentage of the desirable seeds 

 contained or to determine the percentage of impurities regardless 

 of their kinds; and (2) to determine the kinds of impurities and 

 the percentage of each present. In either case the determination 

 is based upon the analysis of only a pmall sample, which is usually 

 prepared by mixing well a handful or more of seeds taken from 



