SEEDS AND SEEDING 69 



very simple germinators, such as in a box of sand, or be- 

 tween two moist cloths in a covered dish. Grass seeds 

 are, however, more exacting in the conditions they require 

 than most other farm seeds, so that misleading results 

 may easily be secured. 



The length of time required by different seeds to ger- 

 minate also varies widely. With most sorts ten days is 

 sufficient time to allow, but many grasses require twice 

 this amount of time. 



60. Actual value of seed. The real or actual value 

 of seed for sowing can be determined only when its purity 

 and viability are known. It is the product of the purity 

 multiplied by the viability, both expressed as percentages. 

 Thus, if the purity be 90 per cent and the viability 80 

 per cent, the actual value or percentage of good germinable 

 seeds is 90 times 80, or 72 per cent. One reason why rates 

 of seeding recommended by different authorities vary 

 so widely is due to the difference in the actual value of 

 the seeds used. 



61. Superiority of local seed. Numerous European 

 experiments with grasses and clovers show as a rule that 

 locally grown seeds give superior yields to those brought 

 from a distance. In the United States this phenomenon 

 is well known in the case of highly bred crops like corn, 

 but has obtained little recognition in the case of grasses 

 and clovers. Results with these crops are particularly 

 instructive, as they have not been subject to artificial 

 breeding, and hence the differences they show may fairly 

 be considered due to natural selection or local adaptation. 

 With most other crops, the factor of difference in variety 

 enters the problem. 



The amount of evidence on this subject is insufficient 

 for final conclusions, but it tends to uphold the generaliza- 



