F. KiDD AND C. West 3 



PHYSICAL TREATMENTS OF THE SEED. 

 (a) High Temperatures. 



Experimental work in which seeds in the air-dry condition have been 

 submitted to high temperatures falls into three categories. 



It has been established that in the case of many seeds the capacity 

 for germination, though low after the harvest, increases during storage 

 to its full value, which is attained by the following spring. A typical 

 example of the results obtained by Attcrberg(2) in the case of barley is 

 given below (Table I). 



Table I. 



Barley reaped at four stages. 



It has been shown by numerous workers {e.g. Hotter (16); Velten(36); 

 Atterberg(2), and others) that if the seeds are exposed for a short 

 time to relatively high temperatures during the period of low germination 

 they at once attain their full capacity for germination {cf. Table II). 



Table II (after Atterberg), 



Kind of .seed Treatment of the seed Result of germination test 



I Dried for 2 days at 37° C. Gave 22 % germination in 4 days 



Barley 



4 „ „ „ 50% „ „ 12 



6 „ „ „ 98 % „ .,, 10 



8 „ ,. „ 99-5% „ „ 8 



I The control seed (untreated) gave only 4 % germination 



We have here a definite experimental result, but a full explanation 

 of the underlying causes of the change which occurs during storage and 

 which is accelerated by heat is as yet not forthcoming, neither, so far 

 as we have been able to find, are there any records extant as to the 

 influence, if any, this procedure exercises upon the development and 

 final yield of the plants produced. 



1—2 



