io8 
WM. CROCKER 
The intact seeds of both these species are dormant when harvested. 
Alisma plantago remains so for years unless acted upon by some of the 
agents mentioned below, but Amaranthus in great part loses its 
dormancy after 2 or 3 months of dry storage. This "so-called" after- 
ripening in Amaranthus seems to involve hysteretic changes in the 
colloids of the coats by which they fall in elasticity or breaking 
strength. This hysteretic effect will be discussed under secondary 
dormancy. 
Certain temperature relations of after-ripening in Amaranthus 
are of great interest. Temperatures above 40° C. will produce some 
germination in the ripe seeds harvested from green plants, and the 
minimum temperature falls as after-ripening progresses. Even fully 
after-ripened seeds have their minimum temperature lowered by 
removal of coat restrictions. As is true of gels> generally, the viscosity 
of gels of the coats lowers with rise of temperature and with it the 
breaking strength falls. The combined action of the hysteretical 
changes of the coat with this temperature effect on their breaking 
strength seems to explain the minimum temperature changes accom- 
panying after-ripening. 
Any treatments that greatly weaken the coats without injury to 
the embryos are good forcing agents for the dormant seeds of both 
Alisma and Amaranthus. Abrasion by various means, carbonizing 
with sulfuric acid or treatment with a great range in concentration of 
acids under proper adjustment of time are effective in Amaranthus. 
In addition bases are good forcing agents for Alisma as well as Sagit- 
taria. The place and method of action of acids and bases as forcing 
agents have been variously interpreted. Fischer^^ found that the 
seeds of Sagittaria and some other water plants, which normally lie 
for years in water in a dormant stage, are readily forced by acids and 
bases. He believed that rapidly diffusing hydrogen and hydroxyl 
ions produce differences in potential thus arousing the dormant 
embryo. 
It has since been shown that the embryos are not dormant and that 
the action is mainly upon the rather consistent gels of the coats leading 
to a mechanical weakening of these. This mechanical weakening is 
probably brought about by two means. As for gels quite generally 
acids and bases increase water absorption and thus lower the breaking 
strength in accordance with the law mentioned above. The coats 
22 Fischer. Ber. Deutsch. Bot. Ges. 15: 108. 1907. 
