AN ARTIFICIAL OSMOTIC CELL 45 



contact with the medium in the canalicular formation than 

 upon the floroid, the former produces the more certain re-growth. 



After a well-developed surface growth has formed, if a fresh 

 supply of mediuni is poured into the vessel, new stems regularly 

 sprout forth from the old surface formation thus submerged. 

 By adding solution each time to the height of only 2 or 3 cm. 

 in a test tube, it is possible to produce a number of surface 

 formations, both canalicular and floroid, one mounted upon the 

 other (see fig. 2, C). 



A structure resembling the floroid described above may be 

 obtained on a glass slide. Crystals are placed upon the bottom 

 of a suitable vessel, brimful of the medium, and the stems are 

 allowed to grow upward, toward the surface, in the usual way. 

 The glass slide is laid across the top of the vessel, thus being 

 in contact with the solution. Upon reaching the surface of 

 the slide, the stems branch out laterally and continue to grow 

 on the glass to which they adhere. The slide may be removed, 

 and the preparation thus obtained may be treated like the 

 slide preparations described above. 



As the stem grows upward, in the regular way, it is observed 

 that a brownish fluid continuously issues from its tip, rises, 

 and becomes dispersed in the upper layer of the medium. If 

 part of the medimn be removed so as to expose the stem for a 

 centimeter or two, and if water is then added until the stem is 

 once more covered, it is observed that instead of the brownish 

 fluid a clear solution of KMn04 issues from the tip of the grow- 

 ing tube. At the same time growth is suspended. If the tip 

 of the stem be exposed and a glass capillary tube be placed over 

 it, the glass tube soon fills with a concentrated solution of KMn04. 

 When the stem is grown in a space about 0.1 mm. in width 

 (somewhat less than the diameter of the stem), as betw^een a 

 slide and a cover glass joined by a frame of cigarette paper, 

 the opposite sides of the osmotic growth — those m contact with 

 the glass — are imperfect. It can then be plainly seen that the 

 canal of the stem is filled with an upward flowing solution of 

 KMn04, and that the solution, as it issues from the tip of the 

 stem and comes in contact with the reducing medium, turns 

 brown. 



