428 THE BIOLOGY OF FLOWERING PLANTS 



The presence or absence of light is not necessarily an 

 absolute bar to germination, and the action of light is not 

 independent but is deeply affected by the temperature 

 relation and other conditions. 



Ottenw alder (19 14) showed that in some cases a sur- 

 prisingly low intensity of light was effective ; germination 

 of Epilohium roseum took place at 25° C. in light of 1/400 

 candle-power. Lehmann (igiSa) investigated this point 

 more fully and found that continuous illumination was not 

 necessary, and that the amount of light required for the 

 germination of Ly thrum Salicaria was extremely small, as is 

 shown in Table XXXVI . 



TABLE XXXVI 

 Relation of Light to Germination of Lythrum Salicaria 



Ottenwalder (i9i4),and Lehmann and Ottenwalder (1913), 

 found that acids, and proteolytic enzymes activated the ger- 

 mination of "light" seeds in the dark. Gassner (1915 b 

 and c) obtained germination in the dark of various " light " 

 seeds with nitrates and nitric acid — which acts as a nitrogen 

 compound, and not as an acid — though with others there was 

 no such result. Lehmann (19 19) obtained germination in 

 light of the " dark " seed of Veronica Tournefortii in potas- 

 sium nitrate. Hesse (1923) found all " light " seeds to 

 germinate in the dark with nitrogen compounds, including 

 those with which Gassner had failed. Some few are also 



