66 Diffusion and Osmotic Pressure 



course it ia possible that, in these cases, the substance in 

 question does not pass the protoplasm as such, but is modified 

 at the surface of the ectoplast and penetrates in another 

 form. For this question there seems to be as yet no method 

 of attack. Wortmann' believed he had evidence that the 

 starch in the endosperm of seeds was not acted upon by an 

 enzyme but by the protoplasm itself; this, however, has been 

 disproved.'' Since protoplasm contains so many enzymes of 

 one sort and another it seems impossible to gather evidence 

 as to whether a given action takes place within the proto- 

 plasmic mass or outside of it. It is probable that it occurs 

 wherever the enzymes are present, whether this be within 

 or without. 



The penetration of anilin dyes has been studied exten- 

 sively by PfefPer,' who showed, for example, that the sap of 

 living cells may be strongly stained by the inward diffusion 

 of methyl blue, methyl violet, etc. Certain anilin dyes may 

 be absorbed into the living protoplasm itself and held there 

 so as to give a marked stain. Even the nucleus may be so 

 stained while living by means of dahlia, mauvein, etc.* 



In most of these experiments there is an accumulation of 

 the stain in the vacuole or within the protoplasm. Thus, if 

 plants of Elodea canadensis be placed for several days in a 

 weak solution of methyl blue, they become visibly stained, 

 while the external solution loses its color. Examination 

 shows that the protoplasm itself is not colored, but that the 



' J. WOETMANN, " Ueber den Nachweiss, das Vorkommen nnd die Bedeutnng des 

 diastatisohen Enzyms in den Pflanzen," Bot. Zeitg., Vol. XLVIII (1890), pp. 581 ff. 



2B. Hansteen, "Ueber die Ursachen der Entleerung der Eeservestoffe aus 

 Samen," Flora, Vol. LXXIX (1894), pp. 419-29. 



3 Pfetfeh-Ewaet, Physiology of Plants, Cambridge, 1900, p. 96. References to an 

 extensive literature are there given, the most important of which is: W. Pfeffee, 

 "Ueber Aufnahme von Anilinfarben in lebenden Zellen," Unters.ausd. bot. Inst. zu 

 Tubingen, Vol. II (1886), pp. 179-331 ; see also E. Oveeton, " Studien ttber d. Aufnahme 

 der Anilinfarben durch die lebende Zelle," Jahrb. f. wise. Bot, Vol. XXXIV (1900), 

 pp. 669-701. 



* D. H. Campbell, " The Staining of Living Nuclei," Unters. aus d. bot. Inst, zu 

 Tubingen, Vol. II (1888), pp. 569-81. 



