ON PLASMOLYSIS. 153 



In an early work by Pringsheim^ a description is given of 

 the process of plasmolysis, in which (|)p. 12, 13) he compares 

 the separation of the protoplasm from the cell wall with the 

 separation of a sticky substance from a membrane to which it 

 had hitherto adhered. He further notices the way in which 

 the protoplasm remains here and there adherent to the 

 cell wall, while sometimes, though separated almost entirely 

 from the wall, it remains connected with it by isolated threads 

 of protoplasm. He goes on to describe how these strings, after 

 undergoing various changes of form, finally break off (cf. his 

 Taf. iii, figs. 16 — 21). 2 Naegeli (* Pflanzenphysiologische 

 Untersuchungen,' 1855, Heft 1) also observed and described 

 strings of protoplasm which connect the contracted proto- 

 plasmic body with the cell wall in plasmolysed cells. He 

 observed them in various instances (epidermis of petals, Spiro- 

 gyra, &c.), but did not recognise their appearance as of general 

 occurrence (cf. his Taf. i, 23; Taf. ii, 2-6; Taf. iii, 4, 5, 12). 

 He also notes in Spirogyra that strings are often attached at 

 corresponding points on opposite sides of the wall, but leaves 

 it an open question whether this is significant or not. 



Hofraeister^ describes the appearance of the contracted pro- 

 toplasm of cells with large vacuoles (p. 8, &c.) as lying free in 

 the cell cavity, but makes no mention of any connecting pro- 

 toplasmic strings as of general occurrence, though (p. 15) he 

 notices the occurrence of such strings connecting the con- 

 tracted protoplasm of cells of certain Algae with the terminal 

 walls. 



It is to H. de Vries* that we owe the most extended treatment 

 of the subject of the action of dehydrating reagents upon the 



' ' Bau und Bildung der Pflanzenzelle,' 1854. 



2 From his description and figures, I conclude that Pringsheina has only 

 seen the coarser strings to be described below. As I there point out, how- 

 ever, the difference between these and the finer strings, which appear to have 

 escaped his observation, is only one of degree. 



3 ' Die Pflanzenzelle,' 1867. 



•* ' Unters. iiber die Mechauischeu Ursachen der Zellstreckung.' Leipzig, 

 1877. 



