458 BOTANICAL GAZETTE [DECEMBER 
to the protoplasmic characters of the embryo, which are supposed 
to be changed so that the seed becomes more active or less active 
by exposure to light. The uses of such terms as “‘lichtmiide” 
and ‘“‘dunkelhart” as applied to protoplasm gives one the charac- 
teristic viewpoint. 
Very recently GassNER (9, 10) has studied the effect of light 
on the germination of some South American Gramineae. His 
interpretation is in harmony with that of K1nzet, the effect of the 
light being considered as exerted upon the embryo. 
In none of these recent investigations have the methods been 
sufficiently refined to locate with certainty the cause of the delay. 
Before the real truth'in regard to the cause of delay in many of 
these instances can be ascertained, more exact and analytical . 
methods of procedure must be brought to bear upon the problem. 
A careful reinvestigation of some of these cases will not only’ 
probably locate the causes, but also reveal the nature of the causes 
of delay. 
Materials and methods 
This investigation of the germination of the seeds of X. penn- 
sylvanicum and X. glabratum was undertaken after the discovery 
had been made that the oxygen pressure necessary for germina- 
tion with testa removed was lower than the results CROCKER 
obtained with them intact would seem to indicate, and with the 
knowledge that the seeds of some higher plants, as Alisma, Eich- 
ornia, rice, etc., could germinate in entire absence of free Oz 
Seeds were collected in various places. Those used during the 
first season were secured in vacant lots in and near Chicago during 
the spring of 1909. One lot of seeds had been collected in the 
autumn as soon as ripe, and were kept in cool dry storage during 
the succeeding winter and spring. During the second season, 
seeds were used which had been collected in Lexington, Ky., in 
November 1909, and kept in an unheated dry room until June 
1910. These seeds would all be included in Gray’s X. canadense 
Mill., but Brirron’s treatment of the genus is certainly more 
satisfactory than Gray’s, and I use the names X. pennsylvanicum 
Wallr. and X. glabratum Britton as in the Brirron Manual. I 
am indebted to Dr. J. M. GreENMAN for examining the seeds and 
