1921] GARDNER~GERMINATION 259 
cris pus and include the seeds of Oenothera biennis as being benefited 
in germination by acid treatment. Why the seeds of Oenothera 
biennis germinate better after treatment with H, SO, and not by 
abrasion is unexplained. 
Temperature and light 
OTTENWALDER (40) claimed that within the range of tempera- 
tures which permit germination, light can be substituted for heat 
at low temperatures and heat for light at high temperatures. With 
Verbascum Thapsus and other seeds he found that germination 
occurred at high temperature in darkness and at low temperature 
TABLE VI 
| Temperature centigrade 
Seeds | 10° | vas | 19° | 24° ar 30° | 35° | 40° 
. Light 
Nicotiana Tabacum......| 0 ° 23 62 55 pe ee, A Es 
Verbascum Thapsus. . Lat ° ° ° 47 82 Ws Ban need Eee as 
MUCUS LATOR ie ° 12 21 36 33 BE etek teenies 
Ochothera biewmis oS: ° ° Maen lleeds Vii Ce ras pipes 
Rumez crispus:......... ° I 42 65 22 Ae eos oor 
Darkness 
Nicotiana Tabacum. ° ° ° II 6 2 ° fe) 
Verbascum Thapsus. . Deen ° ° ° 7 14 15 3 I 
Daucus Carota.......... fe) 4 7 16 12 12 ae Be 
Oenothera biennis. .... .. ° ° ° 5 4 2 id | - 
Rumex crispus.......... ° I 3 8 8 4 set 
in light. In order to test this for American Verbascum Thapsus 
and to see whether it is generally true, the different seeds under 
investigation were placed to germinate in light and darkness at 
different temperatures. It was not possible to control closely 
temperature and prevent small fluctuations. These changes of 
temperature were never sudden, however, and had no effect except 
to increase slightly the percentage of germination in both light and 
darkness. The data reported represent results obtained from five 
different sets of determinations. Seeds were placed to germinate in 
Petri dishes on filter paper wetted with distilled water at tempera- 
tures indicated in table VI and allowed to incubate for 9 days. 
