ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 515 



two former the pieces should not be immersed longer than 12 hours, in 

 the latter not more than one. Paraffin impregnation was effected by 

 means of chloroform or in vacuo ; for the preliminary stages the melting- 

 point of the paraffin was 42°, for the final 55°-60°. The sections, 3-10 /x 

 thick, were best stained with magenta-red and indigo-picrocarmin, 

 safranin and indigo-picrocarmin, or safranin and light-green. After 

 fixation in Bouin's fluid hematoxylin, followed by some contrast stain, 

 such as picro-fuchsin or eosin, gave good results, as also did picro-indigo- 

 carmin and Mayer's carmin. 



Demonstrating the Autolysis of Mitoses.*— Ad. Oes treated the 

 material (root-ends, young anthers, etc.) in the following manner : 

 They were incubated at 32°-40° C. in toluol or chloroform "water (|-| 

 vol. p.c.) with or without the addition of neutral salts (usually \ p.c. 

 ordinary salt). Instead of toluol or chloroform-water, carbolic acid was 

 sometimes used, and in place of NaCl, the nitrates of potassium and 

 sodium were employed. In some cases small quantities of acids or 

 alkalies were added. The best results were obtained at 38° C. with 

 toluol water, to which h p.c. NaCl was added. After £-24 hours the 

 objects were fixed in various media, of which Kleinenberg's picro 7 

 sulphuric acid and the strong Flemrning's mixture were mostly used. 

 The material was stained with safranin and gentian-violet, Delafield's 

 hematoxylin, Heidenhain's iron-alum-hasmatoxylin, fuchsin, acid- 

 fuchsin, and others. 



Bleaching Technique.!— P. Mayer mentions a commercial solution 

 of peroxide of hydrogen which is a very powerful bleaching reagent. 

 Mixed with water or alcohol it gives off oxygen copiously, and still 

 more energetically on the addition of a little potassium iodide. The 

 bleaching power was tested on natural pigment and on tissues blackened 

 with osmic acid, and its action compared with that of other reagents, 

 such as hydrochloric acid and potassium chlorate, chlorine water, and 

 Alfieri's method. 



Hydrogen peroxide has a great tendency to cause the section to 

 be separated from the slide, especially when the action is energetic, as 

 it is when mixed with water. If the diluent be alcohol, then the action 

 is not sufficiently strong. 



Alfieri's method consists in treating the sections with permanganate 

 of potassium (1 : 2000) until they become brown, and then dissolving 

 out the oxide of manganese which has been precipitated in the tissues 

 with oxalic acid (1 : 300). The process is repeated if the bleaching is 

 not sufficient. As the oxalic acid is not altogether harmless, it should 

 not be allowed to act longer than is absolutely necessary. 



Chlorine water is often simpler and more convenient in its applica- 

 tion than the author's cherished mixture of hydrochloric acid and 

 potassium chlorate. 



All these solutions appear to act quite as well before the paraffin is 

 removed from the section as after. 



* Bot. Zeit., lte Abt. (1908) pp. 89-117 (1 pi.). \ 

 t Zeitschr. wiss. Mikrosk., xxiv. (1908) pp. 353-6. 



2 M 2 



