t92t] GARDNER—GERMINATION 253 
of Ranunculus sceleratus and Oenothera biennis as favorably influ- 
enced by light and by inorganic salts containing nitrogen, through a 
wide range of concentrations. OrrENWALDER (40), working with 
Epilobium hirsutum seeds, found that the light requirement as 
regards intensity is closely related to temperature, the former 
increasing as the latter is lowered. The illumination period is 
related also to the temperature, but more closely to light intensity. 
Light-sensitive seeds are also favorably and strongly influenced 
by weak acids. The hypothesis of a catalytic influence of light 
is said to have received support from these observations. 
Materials 
A preliminary examination of 115 samples of seeds collected 
from Shaw’s Gardens, the Botanical Gardens of the University of 
Michigan, waysides, swamps, and fields indicated the following as 
available for the study of the effect of light in germination: Daucus 
Carota, Nicotiana Tabacum, N. sylvestris, N. affinis, Nicotiana 
hybrids, Gentiana Saponaria, G. pannonica, Oenothera biennis, 
Verbascum Thapsus, Amaranthus caudatus, Rumex crispus, Phora- 
dendron flavescens, and Datura Stramonium. Of those mentioned, 
the writer has been unable to find any previous report of light 
sensitiveness of seeds of Rumex crispus, Datura Stramonium, and 
Phoradendron flavescens. Of the light-sensitive seeds not previ- 
ously reported, seeds of Rumex crispus and Phoradendron flavescens 
are favored by light in germination, while seeds of Datura Stra- 
monium are inhibited from germinating by light, as will be shown 
later. 
Jonsson (23) in 1893 reported the seed of Daucus Carota as 
favored by light in germination. Nicotiana Tabacum seeds were 
first reported as light sensitive by RACIBORSKI (43) in 1900. The 
seeds of Gentiana Saponaria, G. pannonica, Verbascum Thapsus, 
and Oenothera biennis were reported as light sensitive by KivzEL 
(24) in 1907. Baar (1) reported Amaranthus caudatus seeds as 
hindered in germination by light. The seeds of Genfiana are not 
conveniently suited to the purposes of this investigation on account 
of the longer incubation period. The seed of Amaranthus caudatus 
are not used because they are light-inhibited seeds. The seeds 
