$14 BOTANICAL GAZETTE [october 



number of water plants ; by reductior 

 minimum necessary for germination 



Xanthium 



. (30) and a number of other Compositae (2), in Chloris ciliata (14) 

 and other grasses, and in Datura Stramonium; and finally, perhaps, 

 by deficiency in salts. To these must be added delays due to 

 embryo characters, as slowness of acid development in the hypocotyl 

 of the haw, apple, peach, and perhaps other Rosaceae. The investi- 

 gation of the mechanics of delayed germination in any particular 



• seed should consider all of these possibilities, and not assume, under 

 the incubus of the overworked stimulus conception with its indefi- 

 niteness and implied inscrutability, that the cause must lie in the 

 embryo. The German investigators, with few exceptions, have 

 been especially prone to the stimulus view and its implication that 

 in characters of the embryo alone dormancy is determined. They 

 of course except the seeds that are known as "hard-coated." This 

 inclination to the stimulus conception is evident in Fischer's (12) 

 interpretation of his results with seeds of water plants. We find 

 Behrens (3) assuming that the pricking of intact seeds has its 

 effect only through stimulus action, and not implying at all the 

 possibility of greater oxygen admission or mechanical weakening 

 of the coats. The same can be said of Kiessling (17) working with 



(rtt with thf> "liaht-hflrde.ned" seeds 



KlNZEL 



of Nigella. 



in their work with light-sensitive seeds, with the 



(14) on Chloris ciliata, the German invest! 



assumed 



* r 



embryo and never upon the coat. One must remember that the 

 coat is most strongly exposed, and that it reduces the light intensity 



he embryo, at least in heavy coated seeds 



It is quite as possible that photochemi- 



in the coat as in the embryo. Neuberg 



group 



like Phacelia tanacetij 'olia 



saccharides, fats, proteins, etc., is hydrolized, and often the com 



transformed 



manganese 



These decompos 



1- 



living substances, so there is no reason for 



