Sect. V, 1922 [51] Trans. R.S.C. 



X. A Study of Induced Changes in Form of the Chloroplasts of Spirogyra 



and Moiigeotia 



By G. W. ScARTH, M.A. 



« 



(Read May Meeting, 1922) 



That the chloroplasts of Spirogyra under certain conditions 

 undergo remarkable changes in form is not a new observation. De 

 Vries/ for example, figured and described many shapes seen by him 

 in natural, untreated, but evidently somewhat pathological material ; 

 Loew- made use of the changes as an indicator of certain toxic action ; 

 Osterhout^ noted contraction under the action of barium and strontium 

 chlorides, regarding it as a specific response (which it is far from 

 being); Chien* extended it to cerium salts but only for one species; 

 while Lloyd, in his Introductory course in General Physiology,^ 

 has set the study of these and other behaviours of the cell as an exercise 

 for students. The nature and meaning of the phenomenon has never 

 been adequately studied, however, although an understanding of it 

 would explain that much is obscure in protoplasmic movement in 

 general. It is believed that the following observations throw some 

 light on the physico-chemical actions underlying this manifestation 

 of so-called irritability of protoplasm. 



The biological material. All the species procurable of Spirogyra 

 exhibited the changes to be described. The size and unusual com- 

 plexity of form of the chloroplasts in this genus render them parti- 

 cularly suitable for study, but similar changes have been observed 

 by the writer in the allied genus Moiigeotia, in mosses and in higher 

 plants. Since in the phenomenon to be described, plasticity is one 

 of the features shown by the chloroplasts, it is necessary to find out 

 whether normally they are fluid bodies. If so, their shape (viz. 

 spirally coiled ribbons with usually a lobed or sinuous outline) is a 

 very unstable one and must undergo change. It has not been possible 

 to detect the slightest modification of outline under ordinary con- 

 ditions of temperature, etc., even after many hours of watching. 

 That slow amoeboid movements may occur in response to certain 

 natural stimuli is quite possible. Indeed, it is well known that the 

 flat chloroplastic band of Mougeotia slowly orients itself with regard 

 to light, while those of higher plants also change position and are said 

 to be amoeboid. That in the case of Spirogyra the chloroplasts are 

 not normally fluid is proved by other than the above merely negative 



