1921] GARDNER—GERMINATION 255 
conditions we can understand the relatively low germination, and 
yet see that light favors the germination of these seeds. 
Seeds of Datura Stramonium were treated as shown in table II. 
Seeds were allowed to incubate for 17 days, and the results indicate 
clearly an inhibitory action of light on their germination. The 
TABLE II 
Percentage Percentage 
Treatment germination | germination in 
in light darkness 
On soll, 26-40" © ici da eae 6 98 
On sand, 36-2109 © os 2 22 
On. filter paper, 90°C... . ° ° 
On filter paper, 24°C. .:...... ° 4 
On filter paper, 30°C. ........ 4 60 
constituents of the soil solution seem to promote materially the 
germination of these seeds in darkness but not in light. Datura 
Stramonium seeds require different treatment from any of the other 
seeds tested, and accordingly are reserved for separate study. 
Light sensitiveness, after-ripening, and viability 
To establish standards for comparison with other data, and to 
indicate the degree of light sensitiveness, various light-sensitive 
seeds were incubated from time to time at room temperature 
- (20-28° C.) on filter paper in light and darkness respectively. The 
results given in table III are fairly representative of these tests. 
These data indicate what may be expected of the various light- 
sensitive seeds under investigation when subjected to germinating 
conditions at room temperature 20-28° C. on wet filter paper in 
Petri dishes. It appears that the seeds of some kinds of tobacco 
are less light favored than others (3. Nicotiana affinis, 108. N. affinis, 
t. Nicotiana hybrid, and 117. Pennsylvania Havana tobacco). 
The results also indicate that not all of the seeds under investigation 
are entirely dependent on light for germination. A certain per- 
centage of each lot of Rumex crispus and Daucus Carota seeds 
usually germinates in darkness. It is also noteworthy that seeds 
of Oenothera biennis do not always germinate, even in light. The 
seeds under investigation seem to retain their light sensitiveness 
