1921] GARDNER—GERMINATION 267 
nation. Perhaps better illumination of the injected Oenothera 
biennis seeds made possible the increased germination reported 
by De Vrigs. 
Increased oxygen supply 
In his investigation of the delayed germination of seeds of 
Xanthium, CROCKER (7) found that the seed coat excludes oxygen, 
while SHULL (46) found a very definite relation between the oxygen 
supply and. the percentage of germination in seeds of Xanthium. 
In order to discover if increased oxygen supply would promote the 
germination of the light-sensitive seeds in darkness, the following 
experiment was performed. Counted seeds were placed on wet filter 
paper in open dishes and placed under water-sealed glass cylinders 
containing 40, 50, 60, 70, and 80 per cent oxygen respectively 
(table XII). Each cylinder was placed in a dark room at 23-28° C. 
and covered with a light-tight metallic cylinder. 
TABLE XII 
| Percentage of germination in oxygen 
Seeds 
erred 5 ao 
Nicotiana Tabacum............... ° ° ° . ng 
Verbascum Thapsus............... ° ° ° ° . 
mucus Cavota 3 oe . 3 9 15 74 
enithets bets.) ccs oie a I x I 3 
Bumex chlanos. asia Sera Se tea 19 18 23 
A comparison of the germination in darkness in the presence 
of different percentages of oxygen shows an increase of germination 
of seeds of Daucus Carota and Rumex crispus with an increase of 
oxygen supply. Other conditions in each of the cylinders being 
the same so far as known, this must be attributed to increased 
oxygen supply. A similar experiment with higher and lower per- 
centages of oxygen would have been interesting, especially a test 
of germination in 20 per cent oxygen (ordinary air) under these 
conditions. It would probably have given results similar to those 
in 40 per cent oxygen and would have been rather more conclusive. 
The regularity of the increased percentage of germination, however, 
due to increased concentration of oxygen, indicates the reliability 
of the results. Clearly this experiment does not indicate an oxygen 
z 
