164 SUMMARY OF CURRENT RESEARCHES RELATING TO 



dealing with sections of unknown forms or such as are likely to disturb the 

 disposition of parts by coiling or contraction. The young were killed in 

 0-1 per cent, chromic acid solution, to which a little (1 drop to a 1 per 

 cent, solution in a watchglass) osmic acid was added ; they were then treated 

 with alcohol of increasing strength, coloured in toto, carefully dehydrated, 

 and cut by Jung's microtome into sections of 1/120 mm. thick. Staining 

 was effected with alum or borax-carmine ; occasionally combinations of the 

 two gave excellent effects. In a footnote the author remarks that the finest 

 and most precise colorations of nuclei are got with alum-carmine, in the 

 case of molluscs and vertebrates; with Arthropods the coloration is less 

 intense and certain, owing to a peculiar swelling of the tissue. 



Preparing Sections of Stem and Root.* — In his investigation of the 

 origin of lateral roots in Dicotyledons, M. A. Lemaire found that sections 

 simply hardened in alcohol were not available, owing to the contraction 

 of the protoplasm ; and the same objection applies to the use of calcium 

 chloride ; the presence of tannin is also a serious obstacle to their examina- 

 tion. M. Lemaire finds the following process produce good results. The 

 section is first placed in the solution of sodium hypochloride known as 

 eau de Laharraque, until the colouring matters are entirely destroyed and 

 the nucleus and protoplasm dissolved, the cell-walls being left intact. 

 This requires a submersion of from 15 to 20 minutes ; but one to two hours 

 produces no bad effect. The best staining material is then anilin-brown, 

 which he uses as a solution of 3-4 per cent, in absolute alcohol. The 

 preparations after being repeatedly washed in distilled water, are placed in 

 drops of this fluid for some minutes, then immersed in absolute alcohol, 

 and finally in oil of cloves until they attain the desired transparency ; and 

 finally mounted in Canada balsam. Sections prepared in this way are 

 remarkably clear, and may be preserved for a long time. Mounting in 

 glycerin does not answer so well. The process will apply to the study of 

 all merismatic tissues. 



Preparing the Epidermal Tissues of Pitcher Plants.f — Dr. J. M. Mac- 

 farlane states that the difficulty he experienced in getting clean and large 

 pieces of the epidermis from the different surfaces of pitchers induced 

 him to try various methods of preparation. Maceration in caustic potash 

 solution of 2 per cent, strength gave admirable results. The pitchers to be 

 macerated were placed whole in beakers containing the solution, and boiled 

 over a Bunsen flame for from 10 minutes to 2 hours. The pitchers ^of 

 Nepenthes, if young and fresh, had both outer and inner epidermis 

 loosened from the green cellular and fibrovascular systems after about 

 15 or 20 minutes' boiling ; old or dried pitchers required 30 to 60 minutes. 

 By floating them afterwards in clean water both epidermal layers could 

 be detached with great ease. Pitchers of Cephalotus were macerated after 

 10 to 20 minutes' treatment, but those of Sarracenia, Heliamphora, and 

 Darlinrjtonia, except when young and tender, required boiling for about 

 2 Lours, with subsequent maceration for 2 or 3 weeks in water. 



In this way not only could long pieces be obtained for continuous micro- 

 scopic examination of the surfaces, but bottled hand specimens of the entire 

 inner epidermis of Nepenthes could be made, showing clearly to the naked 

 eye the attractive, conducting, and secreting surfaces, with associated 

 glands. Similar treatment of leaves for preparations of hairs, water and air 

 stomata, &c., give equally good results in many cases. 



* Ann. Sci. Nat. (Cot.), iii. (1886) pp. 172-4. 



t Rep. 55th Meeting (1885) Brit. Assoc. Adv. Sci., 188(3, p. 1088. 



