1921] GARDNER—GERMINATION 263 
days, in light or darkness, produces a condition from which they 
do not recover when incubated at 25° C. in light or in darkness. A 
comparison of d with control a, 6, and c indicates that sudden 
Changes from extremes of temperature may delay germination of 
Verbascum Thapsus seeds, that such treatment inhibits the germina- 
tion of a large percentage of Rumex crispus seeds, and that it almost 
entirely inhibits the germination of seeds of Nicotiana Tabacum. 
The results in d confirm the observations on Daucus Carota and 
Oenothera biennis made in connection with b, namely, that some 
limiting factor develops during incubation in darkness at low 
temperature which is not easily overcome. The most noteworthy 
result of this treatment is the complete inhibition of germination 
of seeds of Nicotiana Tabacum. This is in agreement with that found 
in 6. Together these results when compared with the control indi- 
cate a light requirement for Nicotiana Tabacum seeds which is not 
replaced by any: temperature combination tried. 
To summarize, this experiment shows that alternating tempera- 
ture may replace light in germination of Verbascum Thapsus seeds, 
that light is necessary for optimum germination of entire seeds of 
Rumex crispus, although change of temperature in a measure 
replaces light. The results of this experiment indicate that seeds 
of Oenothera biennis and Daucus Carota require light and medium 
temperature for optimum germination, and that incubation at low 
temperature in darkness permits a change which is not overcome 
by transfer to high temperature in darkness. Moreover, in Daucus 
Carota exposures to light at 25° C. did not bring about germination 
of these changed seeds. Incubation of Nicotiana Tabacum in 
darkness at 10° C. did not result in increased percentage of germina- 
tion in darkness. Incubation of Ncotiana Tabacum seeds in light 
at ro° C. promoted subsequent germination in darkness. 
Hot water treatment 
In a further attempt to induce germination in darkness, an 
adaptation of the warm bath method of Motiscu (37) was 
employed. The seeds were counted, wrapped in filter paper, 
inclosed in little bags of cheesecloth, and plunged into hot distilled 
water for 0.25 minute and 0.5 minute respectively. Great care 
