204 LILT H. HUIK. 



Methorls. 



To deal with these questions satisfactorily necessitates that 

 no reliance should be placed on any single fixing method, and 

 therefore the whole of my previous work has been repeated 

 with chemically very diverse fixatives, e. g. 5 per cent, and 

 10 per cent, trichloracetic acid, 5 per cent, and 10 per cent, 

 phosphotungstic acid, osmic acid vapour, picric acid, picro- 

 corrosive sublimate with tannin added, absolute alcohol, 

 Hermann's fluid, Flemming's strong mixture, and Flemming's 

 weak mixture. All these methods fully confirmed what I 

 have stated in my previous paper, so that in pursuing my 

 new research I had every confidence in employing again the 

 methods I formerly used, viz. Mann's aqueous picro-corrosive 

 fixative and Mann's eosin and toluidin blue stain. 



The following substances were placed on vigorous fully ex- 

 panded leaves: — Paraffin, white of egg, Kiihne's pure ampho- 

 peptone, Witte's peptone (albumoses), ammonium sulphate, 

 fibrin, Griibler's fibrin peptone, globulin, casein, nuclein and 

 nucleic acid, milk, calcium phosphate, glutin, leucin, creatin, 

 urea. 



In all cases except that of casein the species of Drosera 

 used was D. rot undi folia, as plants reared in greenhouses 

 cannot be considered normal. 



The leaves after being fed were fixed at intervals varying 

 from one minute up to the time of reopening of the leaves. 

 As, however, in the case of white-of-egg feeding the changes 

 produced after one minute are so remarkable,^ shorter periods 

 varying from 5 to 60 seconds were tried with white of egg and 

 also with pure peptone. 



Unfed leaves were fixed at the same time to serve as controls, 

 and to avoid all errors caused by irregular staining sections 

 of control leaves were always mounted alongside those of fed 

 ones on the same slide. 



It may be well to quote here again a definition of the terms 

 applied by me to the nuclear organs. 



' See previous paper. 



