123 
exhibited by Turgescent Pith in water . 
The following list gives a summary of the general results of 
the experiments, including some which are not given in detail. 
Sunflower. 
Transverse diameter of the pith dimin- 
ishes at once without previous increase 
Ditto. 
Ditto. 
Ditto. 
Ditto. 
Increases, then diminishes. 
Ditto. 
Elder. 
Diminishes at once. 
Ditto. 
Ditto. 
Increases, then diminishes. 
Rhubarb. 
Increases, then diminishes. 
Ditto. 
Ditto. 
Ditto. 
Impatiens Sultani. 
Increases, no subsequent diminution. 
Ditto. 
Ditto. 
Ditto. 
Ditto. 
Ditto. 
Ditto. 
Ditto. 
Diminishes, then increases. 
General Results. The cases above considered fall into 
classes — 
(1) Sunflower, Elder, Rhubarb, in which transverse con- 
traction is the final result. 
(2) Impatiens Sultani , in which no such contraction occurs. 
What occurs under Class (1) must be this. Where the pith 
is placed in water it begins to expand in all directions, but the 
longitudinal extensibility of the cell-walls being much greater 
than their transverse extensibility, an increase in length 
continues long after transverse expansion has ceased, and 
therefore the pith is forced to return towards its original 
transverse dimensions, and becomes narrower. Where, as in 
the case of the Sunflower and Elder, the contraction frequently 
begins at once, it is clear that the difference between the 
longitudinal and tangential extensibility is so great, that the 
tendency to transverse expansion is from the first obliterated 
