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were colored with either Prussian or Turnbull's blue. The plants 

 experimented with were sea Algae, mostly from the family 

 Siphonaceae, such as Caiderpa, Derbesia and Bryopsis, obtained 



t 



at the zoological station at Naples. 



The method of coloring consisted in putting the plants for a 

 few seconds into a solution of potassium-ferrocyanide, then 



rinsing well in sea-water, then dropping them for an instant only 



into a freshly prepared solution of ferric chloride. This process 

 was repeated till the plants assumed a light blue color. 



In order to prove what effect this might have on the life 

 energies of the plants so treated, colored specimens were com- 

 pared with uncolored ones. No difference could be detected 

 between the two classes as to rapidity of growth, motion of pro- 

 toplasm, or form assumed by growing parts. The cell membrane 

 was colored uniformly ; the cuticularized layer a dark blue, the 

 cellulose a lighter color. 



This color disappears in living plants after a few hours, but 

 may be called back again by putting them into a solution oi 

 potassium-ferrocyanide, acidified with pure hydrochloric acid. 

 That the coloring process had produced no change in the quali- 

 ties of the membrane was shown, in that no change could be 

 detected in form, elasticity, ductihty, etc. The ability to assume 

 other forms, wood, cutin, etc., was not changed. 



By watching the disposition of the new particles as the new 

 uncolored membrane was formed, the author believes to have 

 proven beyond controversy that in these sea Algae, both apical 

 growth and growth in thickness of wall takes place by appo- 

 < sition. 



By apical growth is meant here the extension of a wall at the 

 extremity of a cell, by which means the cell is lengthened in that 

 direction. He says this growth takes place as follows: "When 

 the colored plants grow on farther, the points of the young 

 shoots break through the old colored membrane." That is, the 

 old membrane grows thinner at that point or surface where the 

 new is to appear, a new colorless membrane Is laid on by appo- 

 sition, grows gradually thicker, while the old grows thinner, the 

 ■original thickness being thus preserved till at last, the old mem- 

 brane bursts and the new grows on. This, he says, is the so- 



