LIFE SPAN OF SEEDS 



43 



distributed over much of the 1173-day period: Campanula rotundifolia, 

 C. persicifolia, Chenopodium album, Capsella Biirsa-pastoris, and several 

 others. Delayed and time-distributed germination of seeds of wild plants 

 is striking in the results reported in this table. Nobbe and Hanlein used 

 room temperature with relatively little fluctuation in temperature. In the 

 soil out-of-doors in Germany there would be much greater fluctuation in 

 temperature during more than three years of the experiment. 



Table 9. Germination Experiments with Seeds of Various Wild-Growing Plants 



(From Dorph-Petersen) 



Dorph-Petersen -* carried on similar experiments with weed seeds at 

 Copenhagen, using the Jacobsen germinator, but ran them in duplicate for 

 a period of 11 years. One set of germinators was kept in the laboratory 

 and the other on an open porch without heat. In one set of these experi- 

 ments he got much earlier and much higher percentage of germination in 

 the outdoor germinators for Anthriscus silvestris, Primula elatior, and 

 Galeopsis tetrahit, and somewhat earlier and higher for Potamogeton natans, 

 while Datura stramonium gave 99 per cent germmation after eight years 

 (98 per cent during the eighth year) inside and only 2 per cent after 11 

 years outside. In another set of experiments he showed that in the germi- 

 nator on the porch with the wide fluctuations in temperature, there was 

 marked delay and distribution in the germination of weed seeds (Table 9) . 



Why Do Seeds Remain Dormant in a Germinator 



OR IN THE Soil? 



Considering both the indoor and outdoor germinators, Dorph-Petersen 

 had a range of temperatures that cared for one of the very important 

 factors in the after-ripening and germination of dormant wild seeds. As 

 we shall see in later chapters, many seeds require a period in a germina- 



