[scarth] changes in FORM OF CHLOROPLASTS 53 



the difference of initial form, while the more common ellipsoidal 

 plastids in other plants examined may change to spherical, as in 

 Type I, or apparently shrink, as in Type II. 



Which of the above types of phenomenon may occur depends 

 mostly on the strength of the factor employed to produce it. The 

 first results from a mild agent, tending to pass over to the second 

 if long applied, while a strong agent produces the second type im- 

 mediately. Different species also differ in their tendency to one or 

 the other type, while a combination of both types at the same time 

 may also occur. 



Reversibility. — -Remarkable as are the changes in the appearance 

 of a cell they are not necessarily accompanied by its death. Even 

 in the limiting state of type I with the chloroplasts spherical and the 

 nucleus lateral, the cell-membrane may retain its semi-permeability 

 for a long time (as tested by eosin-staining or plasmolysis), while 

 with less pronounced changes the cell may even recover its normal 

 form again. This remarkable result has been established in the case 

 at least of certain salts. For example, some filaments of Spirogyra 

 were kept in M/lOO barium chloride until every cell was more or less 

 changed, from mere smoothing of the chloroplasts up to their assump- 

 tion of the spherical form, most being of a cylindrical sausage-like 

 shape. The filaments were then transferred to tap-water and ex- 

 amined from day to day. After about a week the cells had nearly 

 all resumed their normal appearance, with the exception of a few 

 that had died. The latter were mostly cells in which the chloroplastic 

 band had beaded off into spherical bodies, and even such cells may 

 retain their vitality for a few days. Reappearance of marginal 

 processes is the first sign of recovery. Irregular and grotesque 

 shapes mark the process of reversal to the spiral form. 



The factors. — The specific action of the various factors that 

 bring about changes in form is not included in the scope of this paper, 

 but rather the features that are common to all. 



A long series of eperiments has been and is still being carried 

 out on the action of electrolytes, and the conclusions stated later 

 were suggested by the results obtained, a fuller statement of which 

 is postponed. An induction current produces similar changes, type I 

 if mild, type II if strong. It is with this agent alone that rounding of 

 the plastids of higher plants has been detected. Heat (a temperature 

 of 45 C. immediately, and lower temperatures if the exposure is pro- 

 longed) produces both types of behaviour with a strong tendency to 

 the second, as is also the case with other agents that coagulate albumin, 

 such as alcohol, acetone, etc. Other toxic organic substances, such 



