collected by placing metal troughs around the base o£ several trees. The rain water, 

 throughfall, and steraflow collected was stored in plastic containers in a cold room 

 at 3° to 4°C until used. 



Several days prior to the start of this experiment, fresh plant material including 

 green needles, litter, decomposing duff, bark, and roots were collected. These samples 

 were returned to the laboratory, placed in an oven set at 40°C, and allowed to dry for 

 48 hours. All the dried samples except the roots were run through a grinder. The 

 roots were cut into small pieces by hand. The grinder was adjusted so that it would 

 break and crush the dried plant material into smaller pieces but not reduce it to a 

 powder. Each sample was then extracted by placing 225 grams of plant material into 

 2,025 ml of distilled water to give a 10 percent solution (w/v) . The solutions were 

 placed on a shaker for 30 minutes and left overnight, 16 to 20 hours. The plant mate- 

 rial was then removed by filtering through paper. Five percent solutions were made 

 for each sample by diluting (1:1) with distilled water. In addition, two of Hoagland's 

 solutions were prepared, a standard Hoagland's (Ix) and 5x concentrated Hoagland's, 

 to check potential osmotic effects on germination. A total of 16 different test solu- 

 tions was analyzed in this experiment: 10 plant extracts, 3 field rain samples (through- 

 fall, stemflow, rain water), 2 concentrations of Hoagland's solution, and 1 distilled 

 water control. 



The pH was measured for all the test solutions, and the osmotic potential was 

 determined with a Fiske Osmometer for the 10 percent plant extracts, both Hoagland's 

 solutions, and all the rain samples from the field. 



Sterilized cellulose sponges were soaked to water holding capacity in each of the 

 test solutions, and excess solution was allowed to drain off. Each moist sponge was 

 placed into the bottom of a 9.0 cm plastic sterile petri dish and covered with a 7.0 cm 

 piece of filter paper soaked in the corresponding solution. Fifteen stratified and 

 sterilized ponderosa pine seeds were placed on the filter paper. Each petri dish was 

 covered and placed randomly into a dark conditioning chamber set at 25°C ± 1°. Ten 

 replications were set up for each treatment. 



This entire experiment was conducted twice, the first time (experiment A) was in 

 the summer of 1974 and the second time (experiment B) in the summer of 1975., The 

 germination time for experiment A was 9 days and in experiment B, 11 days. During the 

 summer of 1974, the stemflow was collected from two different rainstorms. The first 

 storm was a drizzling rain, and the second was a very short cloudburst. The drizzling 

 rain produced a light brown stemflow, and the cloudburst produced a very dark brown 

 solution. Because of the color differences, these two samples were kept separate and 

 each tested independently. The stem flow for 1975 was a combination of samples from 

 several storms. 



In order to better understand the effect that pH might have on germination, a 

 small germination experiment was conducted using three pH solutions, 3.0, 5.0, and 7.0. 

 Twenty-five stratified ponderosa pine seeds were placed on top of a filter paper and 

 sponge previously soaked in the test solutions. Six replicates were made for each 

 solution, and all dishes were randomly placed into a conditioning chamber. The ger- 

 mination was checked daily for 9 days. A one-way analysis of variance followed by the 

 Newman-Keuls test was used for statistical analysis. 



Results and Discussion 



A variety of comparisons can be made between the different solutions tested in 

 this experiment, but the most meaningful for evaluating the presence of a phytotoxin 

 are the comparisons between the plant extracts and the distilled water and "pure" 

 rain controls. In addition, the effect of osmotic potential and pH of the test solu- 

 tions (table 2) should also be evaluated to ensure that they have not produced the 

 experimental responses observed. 



6 



