59 

 Dr. Franck thea read the following paper : 



Germination Tests at Low Temperature, with particular reference to 

 Seeds which are not fuUy after-ripened. 



BY 



Dr. W. J. FRANCK, 

 Director, State Seed Testing Station, Wageningen. 



When, last winter, one of the members of the Committee asked me 

 to deliver a lecture on germination tests at low temperature, I felt that 

 I had to comply with that request, though oiir investigations into this 

 subject cannot certainly be considered at present as being complete; on 

 the contrary, they are still in their early stages. 



However, I felt that it would be useful if I were to give you a 

 brief survey — as well of the positive as of the negative results — attained at 

 Wageningen by germination tests at lower temperatures than are, to 

 my knowledge, in general use in the various seed testing stations, and 

 also with regard to the manner in which we conduct these experiments 

 at lower temperatures. 



I should have liked to experiment a great deal more in order to be 

 able to give you a more complete outline of this subject, but neither 

 time nor room could be put at my disposal for such a purpose, owing to a 

 great rush during the winter and spring campaign and a continued decrease 

 of staff as a necessary result of the difficult economic conditions existing 

 at present. 



So I beg beforehand the clemency of the meeting if that which I shall 

 read to you here does not contain much news for some of you who 

 have also made a study of this subject. 



When we come to the treatment of the subject of germination at 

 low temperatures, a division must immediately be made into two chief 

 groups, i.e., physiologically unripe seeds, and seeds which are fully 

 after-ripened. 



It is especially the first of these groups mentioned in which appears 

 the phenomenon of delayed germination which has formed a subject of 

 study for various investigators, but so far the essential point has not 

 been revealed. 



In consideration of the great importance that this phenomenon of 

 delayed germination possesses in the practice of seed control, I may, 

 perhaps, be allowed to give as short an explanation as possible of the 

 diverse theories and opinions of the chief investigators who have 

 studied this subject. An additional list of literature will, perhaps, be of 

 convenience to those of you who may desire to increase their know- 

 ledge. A short description, following upon this, of the methods of 

 quickening the after -ripening process practised at Wageningen may 

 give you an idea of our work there. 



By after-ripening is understood the complex of changes, either metabolic, 

 chemical or mechanical, which are able to bring about germination in 

 seeds that are dormant, i.e., in a condition in which they are unable to 

 germinate vmder usual germination conditions. This state of dormancy 

 is shown by the circimistance that the seeds, though swollen, do not 

 germinate and still remain undecayed. During the period of after- 

 ripening, certain changes, preceding the growing processes, must occur. 

 Seeds, showing the phenomenon of dormancy, lose this property in the 

 course of a longer or shorter period of time and become fit to germinate 

 under quite the same conditions as those under which, a short time 

 before, none, or only a very small percentage of them, would germinate 

 readily. It is well known everywhere that this phenomenon of delayed 



