On the change of shape exhibited by Tur- 
gescent Pith in water 1 . 
BY 
ANNA BATESON. 
I T is well known that when turgescent pith is placed in 
water it increases greatly in length, but we have no 
accurate knowledge of any changes occurring in the transverse 
dimensions. 
The following experiments, undertaken at the suggestion of 
Mr. F. Darwin, are directed to this question. 
PfefTer (Pflanzenphysiologie, ii. p. 12) points out that it is 
to be expected that a cell-membrane should exhibit different 
degrees of cohesion and of elasticity in different directions. 
He goes on to point out that the filaments of the Cynareae 
are clearly more extensible longitudinally than tangentially. 
Otherwise it would be incomprehensible that the component cells 
should hardly change in transverse diameter whilst increasing 
very considerably in length. £ The cells retain their cylindrical 
shape, whereas if their walls were equally extensible in all 
directions they would assume a tub-like form from the outward 
bulging of their side walls. This is the case with an india- 
rubber tube into which water is forced while the two ends are 
compelled, by being fixed to glass tubes, to retain their 
original diameter.’ 
The well-known researches of De Vries 2 on the shortening 
of the roots of Carum , Dipsacus , etc., also bear on this subject 
because they demonstrate the different extensibility of the cell- 
wall in different directions. De Vries found that portions of 
these roots when placed in water become shorter and at the same 
1 A preliminary note on this subject has appeared in the Proceedings of the 
Cambridge Philosophical Society, vol. 6, part 6, p. 358. 
2 Landwirthschaftliche Jahrbiicher, 1880. 
[Annals of Botany, Vol. IV. No. XIII. November 1889.] 
