MECHANICS OF DORMANCY IN SEEDS 
109 
consist of pectic or other materials rather readily hydrolyzed or other- 
wise decomposed by acids and bases and are mechanically weakened 
by such chemical transformations. 
Fischer found that the transfer of seeds of many water plants to 
foul water, in which abundant growth of bacteria and fungi occurred 
on the coats, aroused them from dormancy. He attributes the effect 
to acids or bases produced by the organism and acting upon the 
embryo. I am convinced that the rather slight forcing effect of 
organisms is due to enzymatic hydrolysis or decomposition of the 
coats and not to the acids or bases produced. In Alisma concentra- 
tions of acids, sufficient to give but slight forcing action, are too high 
to permit considerable growth of the embryo; and in Scirpus and 
Sparganium^i no concentration of acid or base will force germination. 
We should except sulfuric acid (sp. gr. 1.84) which acts as a carbonizing 
agent and produces good germination of the former after nearly 3 
hours' treatment but only abnormal germination in the latter after 
more than 24 hours' treatment. As we shall see later there is a well- 
established case in which the forcing action of the acid is upon the 
embryo. This is claimed as the point of action in light stimulated 
seeds where acids rather generally have the power of substituting 
for light, but this claim is entirely without critical evidence. In 
Amaranthus retroflexus, a light inhibited seed, the acid has its effect 
upon the coat. There is need of a critical study of the effect of acids 
on light sensitive seeds to learn what part of the seed is affected as 
well as the specific nature of the effect in each case. 
As we have already mentioned, seeds of Amaranthus retroflexus 
may lie in moist soil for thirty or more years in a viable dormant 
condition. It is well to mention known and needed investigation that 
may aid in elucidating this phenomenon, for the findings for Ama- 
ranthus probably apply in a general way to seeds of black mustard, 
shepherd's purse, Lepidium and many others, that lie in the soil for 
years in a state of quiescence with the embryo partially or fully 
saturated with water. As aids to keeping the seeds of Amaranthus 
in a dormant condition in the soil there is the extra resistance to 
expansion offered by the soil and the power of these seeds to take on 
secondary dormancy, a matter discussed later. Such seeds are laid 
open to exhaustion of their foods by leaching and respiration. As is 
coming to be found the case for many seeds the coats of Amaranthus 
have a most efficient semi-permeable membrane. This is well shown 
