Seedbed material : duff, litter, litter and duff, opening topsoil, 

 canopy topsoil, silica. (8 subsamples) 



Autoclaved 

 (4 subsamples) 



No treatment 

 (4 subsamples) 



Seed coats 

 sterilized 

 (2 subsamples) 



Seed coats 

 unsterilized 

 (2 subsamples) 



Seed coats 

 sterilized 

 (2 subsamples) 



Seed coats 

 unsterilized 

 (2 subsamples) 



Unopened ** Opened * 



** Unopened Opened 



Unopened Opened 



Unopened Opened 



F-igupe 1. — Artificial overwintering treatments for laboratory seedbed experiment. 



^After stratification, subsamples were placed directly into the germination chamber. 

 After stratification, subsamples were opened, germinants were counted, and the 

 remaining seeds were placed into chamber. 



made for each seedbed material. One half (four) of the replicates for each seedbed were 

 sterilized by autoclaving for 30 minutes. The remaining four replicates were left un- 

 sterilized. Two of the autoclaved and two of the unautoclaved replicates received 

 ponderosa pine seeds that had been treated with a powder fungicide. The remaining two 

 autoclaved and unautoclaved replicates received untreated pine seeds. The seeds were 

 allocated by weight rather than by numbers. This design resulted in four degrees of 

 sterilization in each seedbed; i.e., duff autoclaved and seeds coats sterilized, duff 

 autoclaved and seeds coats not sterilized, duff not autoclaved and seeds coats steril- 

 ized, and duff not autoclaved and seeds coats not sterilized, with duplicate samples 

 for each (fig- 1) • The covered petri dishes were then randomly placed into a dark cold- 

 room at 2° to 3°C for 5 months. 



On April 22, 1975, the petri dishes were removed from the coldroom. It was ob- 

 served that some germination had already taken place within the dishes, so one dish 

 from each duplicated sterilization treatment for each seedbed was opened and the 

 germination percentage determined by counting all the seeds. This, however, was only 

 a partial germination, so in order to determine complete germination, two 15-seed 

 subsamples were taken from the ungerminated seeds. The seeds of each subsample were 

 placed into petri dishes containing a moist sponge covered with filter paper; the petri 

 dishes were covered and placed into a dark growth chamber at 24° to 26°C. The germi- 

 nation was recorded daily for 7 days. 



The other half of the artificial overwintering petri dishes were placed directly 

 from the coldroom into the dark growth chamber set at 24° to 26°C. After a 7-day period 

 the dishes were removed and the percentage germination determined by counting all the 

 seeds . 



16 



