W. J. V. OSTERHOUT 301 



in the case of Laminaria. In Ulva the rate is slower than in Rhody- 

 menia, but Zoster a is in this respect intermediate between Laminaria 

 and Rhodymenia. 



Up to a certain point the death process in Laminaria is reversible. 

 Thus tissue remaining in NaCl 0.52 m until it has lost 10 per cent 

 of its resistance will recover if replaced in sea water. This is also 

 true of Ulva, Rhodymenia, and Zostera. 



According to their effect upon Laminaria substances may be 

 divided into two classes: (1) those which (like NaCl) cause only a 

 fall in resistance, and (2) those which (like CaCl2) cause a rise of 

 resistance followed by a fall. There are great differences among these 

 substances in respect to the eft'ects which they produce, but as far 

 as the experiments have gone these differences are similar in all the 

 plants studied. Thus it is found that the amount of rise in resist- 

 ance and its duration are much less in the case of Mg than of Ca 

 and this applies to all the plants mentioned. 



Rhodymenia agrees with Laminaria in showing a rise in resistance^ 

 in CaClo, BaClo, SrCl2, MnCl2, NiClo, and a greater rise in alum, 

 Ce(N03)3, andLa(N03)3. 



Ether produced a rise in Laminaria and Ulva {Zostera was not 

 studied). In Rhodymenia ether (2.5, 3, 5, and 5.5 per cent by vol- 

 ume), chloroform (0.02, 0.03, and 0.05 per cent by volume), and 

 alcohol (1, 3.5, 7, 8 per cent by volume) added to the sea water pro- 

 duced little or no rise. This is not surprising in view of the fact 

 that these substances always produce less rise in Lami?iaria than 

 does Ca and that even Ca produces very little rise in Rhodymenia 

 (Fig. 1). In respect to recovery from the injury caused by these 

 substances Rhodymenia agrees with Laminaria in that recovery is 

 practically complete in alcohol (if the fall in resistance has not gone 

 too far), but is almost entirely absent in ether and chloroform." 



In general it was found that substances of one class antagonize 

 those of the other, not only in the experiments on Laminaria,"^ but 

 also in the cases of the other plants mentioned. As was to be ex- 

 pected, the most favorable proportions were not always the same for 



^ Osterhout, Bot. Gaz., 1915, lix, 317, 464. 

 " Osterhout, Bot. Gaz., 1916, Ixi, 148. 

 ^ Osterhout, Science, 1915, xli, 255, 



