472 BOTANICAL GAZETTE [DECEMBER 
of the quantitative method. It may reveal differences existing 
in various parts of the seed, which would otherwise remain undis- 
covered, and may in this way lead to results of the highest signifi- 
cance in the explanation of delay in germination. Often only 
quantitative measurements can detect the factors which determine 
the peculiarities of behavior. 
The oxygen pressure needed to initiate germination in Xanthium 
seeds with coats removed is considerably less than would be 
expected in view of the rapid exchange of gases which CROCKER 
found in these seeds with testas intact. However, the amount 
necessary is large in comparison with the oxygen supply needed 
by seeds of many other angiosperms. The question as to whether 
higher plants can grow in absence of oxygen has been much dis- 
cussed recently. Attention was called to the results of TAKAHASHI 
on rice, of CRocKER on Alisma and Eichhornia, of NaBoxicH and 
LEHMANN on the organs of the seeds of many higher plants, in the 
introduction to this paper. Nasoxicu believes that the organs 
of nearly all seeds of higher plants can grow in absence of free O:. 
Xanthium seeds would certainly have afforded him a remarkable 
exception. It is much more probable, from the data now before 
us, that the seeds of the higher plants vary largely in the amount 
of oxygen required for germination, some of them, like Alisma 
Plantago-aquatica, rice, and other seeds which grow in media 
containing little free oxygen, requiring no free oxygen whatever; 
others, like Xanthium, requiring a comparatively large amount; 
with perhaps the great majority of seeds lying somewhere between 
them in regard to oxygen need. Such seeds as water plantain 
stand at the one end of the series, and Xanthium perhaps at 
the other extreme, with all possible intergradations. The exper! 
ments which have been carried on with Xanthium show that some 
seeds require a comparatively large amount of free oxygen, thus 
making each species of seed a problem in itself. There is no one 
behavior for the seeds of all higher plants, as NABOKICH seems 
to believe. 
There are several facts which need to be considered in connec- 
tion with the apparent inconsistency between the results I have 
obtained with Xanthium seeds as to the need for oxygen when the 
