238 Pennington — A Chemico- Physiological 



Another marked and surprising consequence of the 

 growth under the yellow screen, was the almost total elimi- 

 nation of the crystals normally present in such large num- 

 bers. These disintegrate, oxalate and tartrate alike, and 

 finally disappear entirely from the cell. The small frag- 

 ments into which the crystals break are at first angular, 

 then they become rounded off and gradually smaller until 

 they are quite dissolved. What part these substances play 

 in the nutrition of the cell could not be determined, but 

 there seems every likelihood that a solution does take place. 



The protoplasmic pellicle surrounding the cell wall be- 

 comes much reduced in size, and is quite clear and refrac- 

 tive. Few granules are to be seen in it. The nucleus, 

 too, with its suspending threads, is very clear. This pro- 

 nounced refractiveness is most striking, and gives to the cell 

 a starved appearance. Even the chlorophyll bands partake 

 of it, becoming narrow and of a clear pale green tint. 



Treating the long sugar-filled cells with a very dilute 

 solution of iodine in potassium iodide caused a sudden rup- 

 ture of the cell, and the consequent scattering of the cell 

 contents. This rupture was liable to happen to any part 

 of the wall, the cell-plate being quite as frequently pushed 

 ou t— S o breaking up the threads into short lengths, or even 

 single cells— as was the true wall torn. The force was 

 sufficient to break the protoplasmic pellicle, and even to 

 push the chlorophyll bands and the nucleus through the 

 aperture, throwing out the latter, and carrying it for some 

 distance. 



We have here a large cell in which the sugar content, 

 and consequently the specific gravity of the cell sap, is 

 much increased. The osmotic pressure of a sugar solution 

 is comparatively small, while the pressure of the inorganic 

 salt, potassium iodide, is almost twice as great. The sud- 

 denly-increased endosmosis being greater than the proto- 

 plasmic utricle can withstand, it is violently ruptured, 

 tearing also the cellulose wall. 



The culture could never be maintained for more than 



