RESPIRATION AND OXYGEN. 75 



of the young plants of practically all of these, although in some it 

 resulted in a slower rate of growth than in normal air. 



Deherain (1892 : 8) proved that lack of oxygen prevented germina- 

 tion in water by placing seeds in a tube traversed by a current of 

 aerated water. The seeds at the entrance germinated perfectly, 

 while the ones at the other end did not grow and finally decayed, 

 owing to the consumption of the oxygen by the former. 



Ewart (1894 : 215) demonstrated that prolonged immersion in 

 unchanged water greatly reduced germination. While the per- 

 centage varied from 44 for barley to 95 for beans after 5 days, germi- 

 nation failed after 10 days in the case of beans, 14 days for peas, and 

 3 weeks for wheat, barley, and flax. This was confirmed in later 

 experiments (1896 : 185), which also showed that the same seeds 

 retained their viability several weeks longer in sterile water free 

 from oxygen, 



Lopriore (1895) found that pollen-grains form protuberances in 

 pure CO2, but these soon burst; others are unable to germinate and 

 still others burst in it. Pollen-tubes formed in the air and then 

 placed in pure CO 2 burst for the most part. A content of 1 to 10 per 

 cent carbon dioxid markedly promoted the growth of the pollen-tube, 

 but not its turgor-pressure. The latter increased steadily when 

 tubes were placed in air after 20 minutes in CO 2. 



Jodin (1897 : 442) observed that peas submerged in mercury for 

 more than 4 years showed 80 per cent of normal germination, but 

 when submerged nearly 6 years longer, gave but 22 per cent of nor- 

 mal germination and 22 per cent of abnormal, while 56 failed to germi- 

 nate. Seeds of pea and cress gave no indication of germinating in 

 58 per cent CO2. When returned to ordinary air, all the cress seeds 

 germinated within 2 days, but none of the peas, showing that the 

 latter were killed by the gas. It was found that 7 per cent CO2 

 did not hinder or greatly modify the germination of peas, while at 

 13 per cent the radicle appeared only with difficulty and its growth 

 stopped at 2 to 3 mm. At 50 per cent the power of germination was 

 quickly lost, although respiration continued for some time. Peas 

 in stagnant or sterilized water showed only the first stage of germi- 

 nation, while they germinated normally in running water. 



Recent researches.— Maze (1900 : 350) observed that the seeds of 

 most land-plants will not germinate under water, and that immersion 

 soon leads to the loss of the power to germinate. Germination of 

 immersed seeds was produced by thorough aeration of the water or 

 by means of hydrogen peroxid. 



Schaible (1900 : 93) studied the germination of seeds of Phaseolus, 

 Lepidium, Satureia, Vicia and Hortensia under reduced air-pressure 

 of 3 different grades and confirmed the results of Bert to the effect 

 that it was slower and less complete than in the air. 



