4O WEEDS OF THE FARM AND GARDEN 



tion increased from 34^2 to 38 per cent. In wild rye the 

 dormant period was lessened from nine to five days ; the 

 germination increased from 22 to 48 per cent. 



It was found that the longest dormant period was 

 found in those seeds which have the hardest and thickest 

 seed-coats. Some of the ragweed seeds had a dormant 

 period of 152 days, while some seeds of barnyard grass 

 had a dormant period of 178 days. 



The highest average percentage of germination was 

 observed in common mustard, which was 100 per cent, 

 and for the six tests, 90.3 per cent. 



It has long been known that many seeds refuse to 

 germinate until they have passed a period of rest. Nobbe 

 and Hanlein made a study of the seeds of 31 species of 

 weedy plants, continuing the experiment for 1,173 days. 

 A number of these weeds showed germination after a 

 lapse of 1,173 days; among them were Campanula persi- 

 cifolia, silvery cinquefoil (Potentilla argentea), mouse-tail 

 (Myosurus minimus), hoary plantain (Plantago media), 

 and field penny-cress (Thlaspi arvense). 



It would seem that freezing is decidedly favorable for 

 the germination of many weed seeds. Of 65 species 

 planted November, 1908, four species failed to germinate ; 

 of 60 species planted in Decem,ber, 48 failed ; of 63 species 

 planted in January, 44 failed; of the March planting of 

 62 species, 27 failed ; of 59 species planted in April, 46 

 failed ; of the seeds exposed to the weather, 64 species, 

 24 failed to germinate. 



With the closest care and observation there was lack 

 of constancy in the germination, resulting in marked ir- 

 regularities not to be attributed to known causes, due 

 possibly to inherent qualities. 



Germinability of Weed Seeds After Having Been Kept 

 in Compost and Manure. There is a widespread impres- 

 sion that germinable weed seeds may be scattered with 



