278 ^'^ Dougal, 



Aquattcally grown plants with the characteristic thread-like seg- 

 ments continue to be active when placed in a solution one part in two 

 hundred to one part in two thousand of potassium nitrate, with a range 

 of osmotic pressure from two to about seventeen atmospheres, and form 

 a series of leaves passing gradually toward and into the broadly laminar 

 leaves of the nepionic type. Continuance in the solution was followed 

 by a gradual return in the series to tlie finely segmented aquatic type. 

 The reaction was as if the immersion in the solution produced a brief 

 and temporary effect only. Leaves already partly formed in the bud were 

 affected but little, others less developed might be altered to a greater 

 extent. Later the unknown accommodations of the plant having taken 

 place, the return or progression from the nepionic to the aquatic or 

 mature type occurred in the usual manner. 



It seems impossible to ascribe rejuvenation of buds and the for- 

 mation of leaves to any hydration effect, or to any other simple change 

 in colloidal condition which might be described as liquidity or lability. 

 The disturbance resulting in rejuvenescence, like many other striking 

 phases of reaction in plants may be initiated by a wide range of agen- 

 cies, changes in temperature, changes in moisture, alterations in concen- 

 tration of the medium, separation of a segment of the vegetation body, 

 injury to neighboring buds, etc. The direct effect of all of these so- 

 called stimuli would embrace far too wide results to be included in 

 any distinctive colloidal or osmotic reaction. The only allowable suppo- 

 sition is that which refers the entire matter back to modifications of 

 the supply of formative nutritive material. Rejuvenescence in nearly all 

 of the cases described above was connected with an increased supply 

 of nutritive material available for the awakening buds. In some in- 

 stances the increase resulted from the removal of competition. In other 

 cases as in plantlets arising from leaves used as cuttings the material 

 accumulated instead of being translocated. Cuttings in solutions con- 

 taining much potassium nitrate showed awakening of the lateral buds 

 and death of the terminal buds, the osmotic pressure being injurious 

 to the tender tissues of a bud accommodated to a medium of much 

 lower concentration, while the densely granular cells of the latent buds 

 were in a condition to absorb the solution, and make use of it 



Neobeckia is thus seen to exhibit a wide range of diversity in 

 its ontogeny, as indicated by the form and structure of its mature leaves 

 which may be either of the teri-estrial or aquatic type or of an inter- 

 graded structure. Any of these stages may be induced by seasonal 

 changes or by variations in components of the environic complex as 



