EFFECTS UPON GERMINATION 



799 



Knop's solution on the germination of partially after-ripened achenes in 

 darkness at various temperatures: 



Table 1 



After-ripened achenes with the hulls intact yielded results with water, 

 Knop's solution, and soil, as shown in Table 2. 



Table 2 



Temperature, °C. 



Water, % germinated 



Knop's solution, % germinated , 

 Soil, % germinated 



19 



19 



89.5 



87 



24 



17.5 



92 



91 



28 



14 



85.5 



81 



33 to 34 



14.5 



83 



77.5 



Calcium nitrate was the constituent of Knop's solution that forced 

 germination in darkness. The chlorides, sulphates, and phosphates had 

 no effect on germination except an injurious effect at high concentrations. 

 All nitrogen compounds tested (ammonium salts, various nitrates 

 and nitrites, nitric acid, and urea) were effective in forcing Chloris 

 achenes in darkness and Gassner believed the stimulating action of soil 

 was due to the soluble nitrogen compounds it contained. The best 

 concentration of KNO3 was about 0.05 mol., and of HNO3 between 

 0.001 and 0.01 mol. The minimum effective concentration of the 

 N compounds ranged from 0.001 to 0.0001 mol. 



Nitrogen compounds favored the germination of light-favored seeds 

 of Ranunculus sceleratus and Oenothera biennis in darkness if certain other 

 conditions were supplied. According to Gassner, acids do not substitute 

 for light in these seeds, although they do in Epilohium hirsutum (68) 

 and some others. Gassner spoke of two classes of light-favored seeds: 

 those in which nitrogen compounds replaced light and those in which 

 acids replaced light. 



Gassner (27) studied the permeability of the coats of Chloris ciliata 

 achenes to iodine and KNO3. Iodine in water solution entered the coats 

 rather readily, the coats at the embryo end being more permeable than 

 at the distal end. On the other hand, KNO3 in water solution did not 

 pass through the intact coats of the achene at all. The experiment 

 showed that nitrates substituted for light as a germination promoter 

 without actually entering the living part of the achene. This fact was 

 important to Gassner in shaping his explanation of the mechanics by 

 which light and darkness modify the germination of Chloris achenes. 



