TENSION PHENOMENA OF LIVING ELEMENTS. 12~ 



this way increase in electric conductivity was produced by stimu- 

 lation of a point outside the path of the current. 



\Yhereas many plants are very sensitive to sudden and extreme 

 changes in osmotic pressure, Osterhout 1 found that certain marine 

 alga- thrived when subjected daily to a change from fresh water. 

 to si a water evaporated down until it crystallized out, and vice 

 versa. He does not state whether these algae survive extreme 

 plaHno]v,js : or whether they are so easily permeable to salts 

 as ii"t t. I..- plasmolyzed by the saturated sea water or burst 

 1>\ tin- fre-h water. 



Foi rej 'il.u ion to slight changes in the osmotic pressure of the 

 m< dium. .i change in size of the cell altering the turgescence, or 

 ti nsion <>! the cell wall, is sufficient. 



If / . iitia cells are placed in a hypotonic solution, they 



begin to -\\ell. But soon crystals of calcium oxul.tu are formed 

 in the cell -ap, and in this way the turgor, due chielly to oxalic 

 .K ill. i- redinvd. 2 It would be interesting to know wh.it i- the 

 source <>f the Ca. Was it previously in combination with pn>- 

 teids? 



Tin nmodation to a hypertonic medium take-, pla<< , ac 



iin^ to van Rysselberghe, parth through ab-.o. pi inn of 

 Mil>-',c : the medium and partly through metabolic produc- 



tion oi . -iiiitic substances, chiefly the transformation of >uuvh 

 into ox.ilic .1. 



Ill BlO-ELECTRICAL PHENOMENA. 



I. /;/ P hints. 



( hai .< in permeability of the plasma membrane to ion- \\otild 

 necessarily cause electrical change due to its inlhu-iu on the 

 migration of ions. These electrical change- actually occur, and 

 may be ea-ily studied. 



Stimulation or wounding in plants is accompanied by an elec- 

 tronegative variation of the affected suiface. This negative 

 region spreads in all directions over the surface, but the rate of 



1 I *niv. of Cal. Pub.. Bot.. 1906. II.. 227. 



Jic. Mem. d. 1'Acad. royale de Belgique, 1899. LVIII.. i. 

 1 Compare von Mayenberg Jahrb. f. wiss. Bot.. XXXVI., 381. 



