Aug. 14, 1916 



Agricultural Value of Impermeable Seeds 



779 



EFFECT OF ALTERNATIONS OF TEMPERATURE ON THE GERMINATION OF IMPERMEABLE 

 CLOVER AND ALFALFA SEEDS 



Seeds remaining impermeable after from 4 months to over 1 2 months 

 in wet blotters were kept in a chamber at room temperature for 49 days. 

 The seeds were then kept for 50 days in chambers which, during a large 

 part of the time, were heated daily to about 30 C. and then allowed to 

 cool slowly to room temperature. Finally the seeds were again kept in 

 chambers at room temperature for 51 days. Table IX summarizes the 

 germination records for these three successive periods. 



Table IX. — Germination of impermeable clover and alfalfa seeds during successive 

 periods of similar length with different temperature conditions 



Kind of seed. 



Number 

 of imper- 

 meable 

 seeds used. 



Approximate percentages of ger- 

 mination during — 



50 days 

 49 days at with ire- 

 room tem- I quent 

 perature. | heating to 

 30° C. 



5 r days at 

 room tem- 

 perature. 



Red clover. . 

 Alsike clover 

 White clover 

 Sweet clover. 

 Alfalfa 



2,382 

 118 

 270 



637 

 230 



25 



The use of the alternating temperatures increased very slightly the 

 germination of red-clover, alsike-clover, and white-clover seed, but did 

 not influence the germination of sweet-clover and alfalfa seed. In no 

 case did more than 1 1 per cent of the impermeable clover seeds germinate 

 in the five months included in the three periods of observation. 



Clover seeds which remained impermeable after various lengths of time 

 in wet blotters were tested for germination at i°C. in an ice box averag- 

 ing about io°, at 20 , at 30 , and with daily alternations between each 

 two of these temperatures. When alternations of temperature were used, 

 the seeds were kept in the chamber at the warmer temperature for about 

 seven hours of each day and in the chamber at the cooler temperature the 

 remainder of the day. In each test a succession of several temperature 

 conditions was used, each condition being maintained for several days. 



Figure 4 shows graphically the results of a series of tests of red-clover 

 seeds from a single original lot which remained impermeable after four 

 days' soaking in water. During these tests many seeds softened and 

 remained for several days after softening at a temperature too cold for 

 their germination. These softened seeds, as well as those which softened 

 at warmer temperatures, invariably germinated later if subjected to a 

 temperature favorable for germination. In order to emphasize the 

 effects of the different temperatures, figure 4 shows only the rates of 

 softening of the seeds without regard to their immediate germination. 



