-— Kations v was agree only to their physi 
expected of periments of lo 
1917] BROOKS—PERMEABILITY 233 
increased exosmosis may be due, not to increased permeability, 
but to increased production —_ the cell of the substance which 
diffuses out. 
Visible changes within the cell 
This method, although sometimes valuable in the Servedtiontion 
of the penetration of substances like the alkaloids which form intra- 
vitam precipitates, and acids and alkalies which cause color changes 
of pigments or intra-vitam stains, has found little application in the 
study of the penetration of inorganic salts. 
OsTERHOUT (39) showed that crystals of calcium oxalate form 
in the root hairs of seedlings of Dianthus barbatus (previously grown 
in distilled water) within a few hours after their immersion in dilute 
solutions of calcium salts, and the subsequent normal growth of 
the cells proved that they were not injured. ENDLER (7) followed 
microscopically the entrance of intra-vitam stains (neutral red and 
methylene blue) into various plant cells under the influence of 
various kations. He also investigated the rate of disappearance 
of the dyes from stained cells, living and dead. The experiments 
are extremely instructive, showing that at 24 OF more hours the 
Passage of dyes through the membrane was increased by kations- ie 
in mie hate orters Na<K< Mg< Ca<Al. Aluminium formed 
+} work f dyes from 
in the ¢ experiments with < dead cells, seen ea 
. tannate formed in the cells. ‘This s 
decrease in ee was Seek = a meee oe 
ae parmint kations, and that this was oa il oo a 
