296 BOTANICAL GAZETTE , [October 



Xanthium as shown by Shull (29), and far exceeds that of the 

 slow imbibing seeds of the grasses as found by Schroder (28). 

 In turn this rate of water intake is considerably exceeded by some 

 of the Cucurbitaceae (32) (Cucurbita ar gyros per ma), where, however, 

 the intake is largely due to a spongy capillary layer in the coat 

 itself. On the other hand, we do not know to what degree the water 

 intake in intact Alisma seeds is due to the coats; it is certainly due 

 to this to a very large extent. 



3. Effect of acids upon rate of water intake by the 

 embryos. — Martin Fischer (13) has found that bases and acids 

 increase the rate as well as total amount of water absorption by 

 colloids. Borowikow (4) has shown that acids increase the rate 

 of growth, or at least the rate of elongation of roots in water; while 

 Promsy (25) and Eckerson (10) have shown that acids hasten 

 the rate of germination of many seeds. These workers attribute 

 the effect of the acids, at least in part, to the fact that they further 

 the hydration of the colloids — in the case of the plant organs, the 

 cell colloids. It will suggest itself immediately that the effect of 

 the acids on the germination of water seeds may be due to their 

 increasing of the imbibition force of the embryo, thereby enabling 

 the embryo to rupture the coat. If this proves to be the case, the 

 interesting situation appears that while the coat is the real cause 

 of the delay, the effect of the acid is upon the embryo itself, increas- 

 ing its imbibition power and enabling it to rupture the restraining 

 coat. To determine this point experiments were made to find 

 the rate of elongation of the embryo in water and in solutions of 

 hydrochloric acid and sodium hydrate of various concentrations. 

 In order to allow free access of the acid solutions and water to the 

 embryo, the coat was removed at both ends of the embryo as 

 described under " material." Only embryos that remained un- 

 injured after the removal of the coats were used in the experiments. 



run with water. 0.01 N HC1 



N HC1 



em 



interv 



A great variation in the rate of elongation of the various emoryo: 

 is shown. This seems to be characteristic of every crop gathered 



individuals 



g low rate ui civi^ 



