27(5 Mac Dougal, 



pressure which would be set up by this solution would be about 35 

 atmospheres. A number of plants grown as aquatics withe mature form 

 of finely divided filamentous leaves, and others which had been culti- 

 vated as terrestrials and formed the mature type of finely dissected 

 leaves were placed in the solution in 1904 The filamentous aquatic 

 leaves were quickly killed, and the plants bearing them were checked 

 and showed no marked activity of any kind during the few weeks the 

 experiment was continued. The individuals taken from terrestrial 

 conditions showed a marked difference in reaction. The finely divided 

 leaves were not killed, but tlie terminal buds which produced them 

 became inactive. At the same time lateral or axillary buds on the 

 terrestrially grown stems underwent rejuvenescence, beginning with the 

 formation of broadly laminar leaves, which merged in a series in which 

 incision and division became more marked. The preparation was taken 

 down before filamentous threads were produced. 



The continuation of the observations upon material from the 

 original introduction resulted in a long vegetative series. Some of this 

 material had been carried to the Coastal Laboratory at Carmel, and 

 was being cultivated as aquatics with the mature filamentous type of 

 leaf -divisions in 1912. Three of the plants were placed in a glass dish 

 containing 1000 ccm of water and 5 gram potassium nitrate on Augusts. 

 The following entries are taken directly from my notebock: 



"Early in September it was seen that the series of leaves included 

 forms which passed by gradual stages into organs with divided laminar 

 segments with fewer incisions until finally organs were produced in 

 which the indentations were entirely marginal and the small but rela- 

 tively broad laminae were those of the nepionic type, which thus had 

 come about by gradual stages rather than as an abrupt reaction." 



It was thus demonstrated again that in Neobeckia as in Sium and 

 Proserpinaca the addition of such compounds as potassium nitrate to 

 a water culture in which aquatic individuals were growing "resulted in 

 the production of primitive leaf-forms in a simplifying series rather 

 than as abrupt appearange following rejuvenescence." 



The interpretation of these reactions involves the whole question 

 as to the nature of the physical changes underlying rejuvenation, and 

 no pretence is made that the facts cited above solve the main problem. 

 The general trend of the evidence afforded by the behavior of Neobeckia 

 for ten years iiowever may be best apprehended when the facts in 

 question are considered in totality. 



