AGRICULTURAI, SEEDS 1607 



Freezing when wet causes the subsequent germination of many imperme- 

 able seeds, but may kill some seeds which had previously softened. 

 Any constant temperature from 34° F. has little effect upon the softening 

 of impermeable clover seeds. Alternations of temperature have but lit- 

 tle effect on the softening and germination of impermeable clover and al- 

 falfa seeds if none of the temperatures used in the alternations are below 

 680 p. 



Alternations of temperature cause the softening and germination 

 of many impermeable clover seeds when a temperature of 50^ F or cooler 

 is used in alternation with a temperature of 68° F or warmer. The effect 

 of such an alternation of temperatures is greatly increased by previously 

 exposing the seeds to germination conditions at a cool temperature (500 

 F. or cooler), and is decreased by previously exposing the seeds to germi- 

 nation conditions at a warm temperature (86° F.) 



Even under the most favourable conditions only a small proportion 

 of impermeable red clover, alsike clover, white clover and white sweet 

 clover seeds produce seedlings promptly when sown in warm weather. 



Impermeable seed? of red clover, alsike clover, white clover and white 

 sweet clover will pass the winter in the soil in a freezing climate without 

 injury. A lea, t 50 or 60 per cent of them may be expected to germinate 

 in the soil the following spring unless some of them germinate during 

 warm weather in the winter. If this occurs, the seedUngs produced ir 

 the winter are liable to be killed by subsequent freezing. 



A large proportion of impermeable lucerne, crimson clover, okra and 

 hairy vetch seeds will germinate in the soil during the first few months 

 after planting, some of them early enough to be of importance to the crop. 

 Nearly all lucerne and okra seeds, even if they are impermeable in the au- 

 tumn, are killed when the}' pass the winter in the soil or on the plants out 

 of doors in a freezing climate. A small proportion of the impermeable lu- 

 cerne seeds survive with their vitality uninjured. Some of the okra seed 

 remain impermeable during the winter, but the majority' even of those 

 which remain impermeable are killed by the winter's exposure. 



The following general rules, based upon the above conclusions and the 

 experimental results, are suggested as guides in agricultural practice with 

 impermeable seeds : 



a) When seed is to be sown in the late spring or summer. 



Consider one tenth of the impermeable seed as good. Add one tenth of the percentage 

 of impermeable seed to the percentage of germination. Calculate from this sum the quantity 

 of seed of the given lot necessary to give the desired cjuantity of good germinable seed. This 

 may be expressed in the form of an equation, thus : 



, , Number of lbs. of good seed desired per acre 



Number of lbs. to sow per acre 



Percentage of germination -f- i/jq percentage of impermea- 

 ble seeds 



For example, suppose it is desired to sow per acre 15 lbs. of viable seed, none of which is 

 impermeable. I'ifty per cent of the lot of seed to be used germinates and forty per cent is 



