2g0 Mac Dougul, The Determinative Action U8W» 



The cultivation of Neobeckia as a terrestrial was accompanied by 

 the development of thickened roots, in which an exaggerated formation 

 of cortical and fibrovascular tissues ensued. Large amounts of starch 

 accumulated in these members, the entire reaction being one which 

 probably does not occur in nature. 



Variations in the form of nepionic leaves have been seen to be 

 coupled with the composition of the medium or substratum, the avai- 

 lability of a supply of food to buds and with competitions. No connection 

 was established between the form of such organs and the stage of the 

 material taken for rejuvenescence, although it is to be said that in most 

 of the experiences such effects would have been masked by other effects. 

 While it is true that most of the diverse structures exhibited by the 

 leaves of Neobeckia show some degree of suitability to the conditions 

 under which they are formed, yet this is by no means always the case 

 as instanced by the occurrence of terrestrial types in submerged plants- 

 This of course is still more noticeable in the various regenerative 

 proceedings in which the form and structure of the leaves are deter- 

 mined by the presence or abundance of certain formative materials. 

 The form and structure of roots, and foliar organs of Neobeckia are 

 seen to be determined by environic conditions to a much greater extent 

 than in Proserpinaca, Sium, or probably any other so-called "poly- 

 morphic" species, yet the reaction to such external agencies is not a 

 direct or physical adjustment. 



