278 
Mac Dougal, 
Aquatically grown plants with the characteristic threacl-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 ränge 
of osmotic pressure from two to about seventeen atmospkeres. 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 the 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 ränge 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 granulär 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 ränge of diversity in 
its ontogeny, as indicated by the form and structure of its mature leaves 
which may be either of the terrestrial 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 
