EFFECTS UPON GERMINATION 821 



C. Some seeds and fruits germinate equally well in light and dark. 

 This is true of the small grains, Zca mays, beans, clover, and many other 

 legumes. Of the 964 species investigated by Kinzel, 35 were indifferent to 

 light. 



D. Several conditions partly or entirely displace the effect of light 

 in light-sensitive seeds and fruits. 



a. After-ripening in dry storage reduces or entirely eliminates the need 

 for light in various light-favored seeds. Poa achenes kept in dry storage 

 for one year germinate almost as well in darkness as in light. After- 

 ripening partially eliminates light need in Chloris, Ranunculus, Epilohium, 

 and Oenothera achenes or seeds. The inhibiting effect of light on Phacelia 

 seeds falls with period of dry storage. 



h. Seed or fruit coats, or the hulls of grasses, increase the necessity for 

 light in the germination of some light-favored seeds. The hulls render 

 Chloris achenes hght-obligate and increase the need for light in Poa. 

 Pricking the seed coats of Oenothera increases germination in dark- 

 ness. The coats also modify the action of light on Hght-inhibited seeds. 

 Removal of the seed coats from Phacelia seeds overcomes the inhibiting 

 effect of light. Pricking the coats causes "lichthart" seeds of Nigella 

 to germinate in part. 



c. A full atmosphere of oxygen forces the light-obligate Chloris achenes 

 with hulls intact to full germination in darkness, and the light-inhibited 

 Phacelia seeds to full germination in Ught. 



d. Knop's solution substitutes for light in a number of light-favored 

 seeds. The nitrate of the solution is effective. The other salts of the 

 solution are not effective. Nitrites, nitric acid, ammonium salts, and 

 urea are also favorable. Nitrates entirely displace the light need of 

 Chloris achenes with hulls intact at temperatures above 22°C. They also 

 increase greatly the germination at temperatures below 22°C., where 

 light inhibits. Nitrates favor the germination of the following light- 

 favored fruits and seeds in darkness: Poa, Ranunculus, Epilohium, 

 Lythrum, and the Gesneriaceae. The light-inhibited seeds of Phacelia 

 and Nigella are not favored by nitrates. 



e. Weak acids substitute for light in part in the light-favored seeds of 

 Lythrum, Scrophula/ia, Verhascum, and Epilohium. 



f. Either daily intermittent or high constant temperatures substitute 

 for light in various light-favored seeds. The most favorable intermittent 

 temperatures give better germination of Poa achenes than light with any 

 constant temperatures. Light and nitrates increase the germination of 

 Poa compressa achenes somewhat at the most favorable intermittent 

 temperatures. Intermittent temperatures replace light w^ith after- 

 ripened Chloris achenes with hulls intact, but not with non-after-ripened 

 or "dunkelhart" achenes. With seeds of Epilohium, Oenothera, and 

 others intermittent temperatures substitute fully for light. 



