Observations on Spirogyra. 429 



To study the relation of the starch granules to the 

 protein crystals, the two best ways are these : — 



1. Detmer's method — 



Spirogyra (preferably Sp. jugalis) is placed in strong 

 warm alcohol, which, in about ten minutes, will have 

 extracted the whole of the chlorophyll. The bleached 

 threads are laid either for a short time in hot, or for twenty 

 hours in cold, not much concentrated caustic potash (a 5 per 

 cent, solution I find best) ; next the threads are carefully 

 washed out with distilled water, then treated with dilute 

 acetic acid to neutralise the potash completely ; again 

 washed in water and placed in a solution of — 



2. Mann's method — 



Treat the threads for two minutes with liquor chlori, and 

 examine at once in liquor chlori. 



Methods for demonstrating the nuclei and threads I may 

 mention here also. 



Nuclei show the endo-nucleoli beautifully if treated with 

 a saturated solution of bichloride of mercury and picric acid 

 in water or in absolute alcohol. Threads treated in this 

 way show hardly any plasmolysis. 



The threads joining the nucleus with the pyrenoids are 

 stained most satisfactorily by placing some Spirogyra threads 

 for three hours into a saturated watery solution of picric 

 acid, to which nigrosine, readily soluble in water, has been 

 added, till a layer, 1 inch thick, is of a deep olive-green 

 colour. Tlie Spirogyra is then washed thoroughly in dis- 

 tilled water to remove the picric acid. The threads and 

 the nucleus will be stained a bluish black, and the nucleolus 

 will be almost black. 



Another equally good method for demonstrating the 

 threads is this : place Sjnrogyra for twenty-four hours in a 

 1 per cent, gold chloride solution, and examine in this solu- 

 tion ; the threads are not stained, but are well defined, having 

 become very refractive. A saturated watery solution of 

 picric acid renders the threads also very evident. 



I may mention here that although, as a rule, the nucleus 



