METHODS OF SPECIAL STAINING ETC. 659 



leaving a channel between them. The material is placed in the 

 channel and covered with a coverslip ; the space is then com- 

 pletely filled with liquid. A strip of linen is then pushed under 

 the cover from each side and rubber bands or clips are used to 

 fasten the coverslip to the slide. The linen strips are connected 

 to a siphon system, one acting as inlet and the other as outlet. 



Gautheret (C. R. Acad. Sci. Paris, cxcviii, 1934, p. 2195) 

 grows explants of cambium and phloem on cotton saturated with 

 culture media. 



See also Rhumbler, Zeits. Wiss. ZooL, xlvi., 1888, p. 549 ; 

 ScHONFELD, J. Roy. MicT. Soc, 1888, p. 1028 ; McCormick, 

 Science, Ixxiii, 1931, p. 131. 



See also under Fungi, methods of Vernon, Bachmann, Cifferi. 



1322. Pollen Mother-cells. Kuwada and Sakamura {Proto- 

 plasma, i, 1926, p. 239) find that the chromosomes in pollen- 

 mother cells of Tradescantia generally cannot be seen in cane 

 sugar. This is the result of over-swelling. The pH especially has 

 a striking effect on the distinctness of the chromosomes. They 

 swell and finally lose visibility as the joH rises from 1-7 to 6-7. 

 The swelling is reversible within wide limits. For Tradescantia 

 the best pH is 5-0, or a little less ; the medium requires to be well 

 buffered, since the anther contents are alkaline and readily 

 affect a lightly buffered solution (see also § 1374). 



Sakamura (Protoplasma, i, 1926, p. 537) made observations on 

 cells mounted in the viscous contents of the anther or in olive 

 oil. Both media are superior to sugar and salt solutions. When 

 mounted in olive oil, very few pollen mother-cells actually come 

 into contact with the oil ; the remainder are surrounded by 

 contents of the anther even when this is small in amount. 



ScHAEDE {Ber. Deutsch. hot. Ges., xlviii, 1930, p. 342) mounted 

 living staminal hairs of Tradescantia in liquid paraffin. See also 

 ScHAEDE, Protoplasma, iii, 1928, p. 145. 



1323. Intravital staining is limited in its application to plant 

 material largely because the firm nature of the cell-wall impedes 

 the entry of the dye. Further, cutin may prevent wetting of the 

 material and the presence of pigments obscure the effect of the 

 dye. Suitable material includes : fresh-water algae ; fungi ; 

 hairs of pistils, stamens, leaves, etc. ; stripped epidermis ; root- 

 hairs ; portions of aquatic plants. Such material can frequently 

 be kept in good condition and stained in an isotonic solution. 

 Suitable stains are Bismark brown in dilution of 1 : 3000, methylen 

 blue and neutral red in dilutions of 1 : 1000 to 1 : 100,000. Such 

 solutions stain the nuclei, plastids, etc., and the stain should 

 become more intense as the cells become moribund. 



See Sands {Science, Ivi, 1922, p. 517) for vital staining of 

 Tradescantia chromosomes. 



Neutral red penetrates more rapidly and is less toxic than other 



