88 THE ROYAL SOCIETY OF CANADA 



needles (Bidens bipinnata L.), failed to germinate. Docks, ragweed, 

 purple cockle, tumbling mustard and peppergrass, were all capable of 

 germination. 



In another experiment a cow and horse were each fed two 

 pounds of the unground grain screenings with middlings, bran, and 

 wheat straw, each morning and night for seven days. On the evening 

 of the seventh day the animals were bedded with sawdust and the 

 dung of one night collected. The sawdust and dung were thoroughly 

 mixed and put in boxes and set on a bench in the greenhouse. The 

 dung was collected on May 24. On June 21, the following weeds had 

 grown : 



Cow Dung Horse Dung 



149 Lamb's quarters 1213 Lamb's quarters 



12 Pigweed 28 Foxtail 



14 Bindweed 11 Pigweed 



4 Foxtail 12 Bindweed 



2 Timothy 6 Timothy 



3 Clover 



2 Morning glory 



5 Mustard. 



Grinding Screenings 



The impossibility of pulverizing all of the seeds when the entire 

 screenings are ground up together by an ordinary chopper is well 

 illustrated by the analysis of a sample that had been ground with the 

 idea of putting it on the market as a feed. One-eight ounce contained 

 the following weed seeds: 



Chenopodium album L 460 



Sisymbrium altissimum L 215 



Camelina sativa (L) Crantz 8 



Potentilla monspeliensis L 7 



Setaria viridis (L) Beauv 6 



Brassica sp 2 



Conringia orientalis (L) Dumort 2 



Thlaspi arvense L 2 



Other sorts 15 



This is equivalent to more than 90,000 weed seeds per pound. 



The complete reduction of screenings containing the black seeds 

 is a difficult and expensive process. It requires specially constructed 

 machines which are difficult to drive, and thus expensive to operate. 

 Often a combination of two or more machines is employed, one of 

 which is usually an attrition mill. The "Perplex" or "Simplex" 

 grinder is also in common use. 



