284 BOTANICAL GAZETTE [APRIL 
Again, the presence of neutral or very faintly alkaline fats in 
the cells of the dry embryos and the development of acids in 
embryos incubated in light and no change or development of slight 
alkalinity when incubated in darkness is very significant. It is 
generally assumed that increased acidity of fatty substances indi- 
cates hydrolysis due to the action of enzymes. If this assumption 
be granted, the admission is necessary that light initiates processes 
which in some way result in increased acidity, which is followed by 
germination, and that where light is not admitted acidity does not 
develop sufficiently to cause good germination. Three explanations 
of how light acts may be offered: (1) light may act directly to 
split the fats to fatty acids and glycerine; (2) light may activate 
the lipolytic enzyme which splits the fats; (3) light may initiate 
some change that produces a little acid which may activate the 
lipolytic enzyme which splits the fats. 
While it is possible and even probable that light can act directly 
on the inclusions of cells to produce such changes as the formation 
of acid, it is hardly necessary to make this assumption. The 
proteolytic enzymes become active in the absence of light when the 
seeds are put under the usual conditions for germination. A certain 
percentage germinate in darkness even though they have not been 
treated with electrolytes or other stimulating agencies. Moreover, 
the amount of acid produced, though small, is relatively more than 
might be expected from the chemical action of light on lipoids. 
The evidence of the existence of lipase rather indicates either of the 
other explanations as much more acceptable. There is little choice 
between light activating the enzyme and light initiating some 
change which produces a little acid which may activate the lipolytic 
enzyme which splits fats. In either case light is the stimulus 
which initiates the changes leading to germination. 
Summary 
t. The seeds of Rumex crispus, Datura Stramonium, and 
Phoradendron flavescens were found to be light sensitive. The 
germination of seeds of Rumex crispus and Phoradendron flavescens 
was promoted by light; the germination of seeds of Datura Sira- 
monium was hindered by light. 
