26 M. H. JACOBS. 



EXPERIMENTS ON SPIROGYRA. 



It was thought desirable to supplement the experiments on ani- 

 mal cells with similar ones on some type of plant cell to determine 

 how general the results already obtained might be. For this pur- 

 pose Spirogyra was chosen, as it had already been successfully 

 employed in a similar fashion by Sziics in his work with aluminum 

 salts, and preliminary experiments showed that CO 2 produces 

 marked differences in the ease with which the chloroplasts can be 

 displaced by centrifugal force. 



The first lot of Spirogyra studied, which was obtained early in 

 the winter, showed clearly both liquefaction and solidification 

 effects just as the Protozoa had done. Unfortunately, before all 

 of the details of these processes could be studied, the material was 

 exhausted and no more could be obtained until the following 

 spring. This latter material, while giving the liquefaction effect 

 with the greatest clearness, for some reason failed to show solidifi- 

 cation except such as was obviously associated with irreversible 

 death changes. The experiments, therefore, leave something to be 

 desired in the way of completeness, but since the results, as far as 

 they go, especially those obtained with the earlier material, are in 

 good agreement with those already described, a few of them may 

 be mentioned briefly. 



In one experiment with the winter material a number of the 

 filaments were placed for 2 minutes in distilled water saturated 

 with CO 2 . When centrifuged for 2 minutes at the same rate as 

 that employed with the Protozoa, and then examined with the 

 microscope, the chloroplasts in practically every cell were found to 

 be aggregated in dense masses at the sides or ends of the cells, 

 according to the position of the filament during centrifugalization. 

 Controls in ordinary distilled water showed a much less complete 

 separation. On the other hand, in filaments exposed for 10 min- 

 utes there was practically no movement of the chloroplasts at all, 

 their spiral form being maintained almost as well as in cells which 

 had been fixed for a few minutes in boiling water before centri- 

 fuging. 



In another experiment filaments of Spirogyra were exposed to a 

 saturated solution of carbon dioxide for 2, 4, 8 and 16 minutes, 



