ZOOLOGY AND BOTANY, MICROSOOPY, ETC. 1085 



starcli iu leaves, can be readily performed according to a method re- 

 cently described by Prof. J. Sachs. To show the starch-grains a leaf 

 must be bleached and made transparent in this way : The fresh leaf 

 is placed in boiling water for ten minutes, after which the chloro- 

 phyll is extracted by placing it in alcoliol. The colour is thus re- 

 moved without rupturing the cells, which retain the starch. The 

 latter is then made visible by treatment with iodine. The cellular 

 tissues become stained dark blue or lighter, according to the quantity 

 of starch present. Comparative experiments may be made by ex- 

 posing half of a leaf to sunshine while the other half is protected. 

 A leaf collected in the evening contains much more starch than in 

 the morning. 



Studying Pollen-grains.* — For the study of the development of 

 the pollen-grains of Campanula Americana,] Prof. C. P. Barnes used 

 alcohol-fixed buds, which had been twenty-four hours iu equal parts 

 of 95 per cent, alcohol and glycerin, commencing with those 2 mm. in 

 length. The sections of the entire bud were stained with an aqueous 

 solution of methyl-blue. The plant is an admirable one for the use of 

 students in this respect. 



For the study of the pollen-grains themselves fresh material is re- 

 quisite. The best results were obtained by staining with Grenacher's 

 borax-carmine. The grains are placed in a drop of 2 per cent, acetic 

 acid, and after a few minutes a drop of borax-carmine added. This is 

 allowed to remain an hour, the slide being protected from evaporation 

 meanwhile. The stain is then washed out with acidulated alcohol 

 (70 per cent, alcohol 100 cc, HCl. 5 cc), and a drop of dilute glycerin 

 })laced on the specimens. The demonstration of the nuclei is ex- 

 tremely difficult. 



The grains were germinated in a hanging drop of 3-12 per cent, 

 sugar solution in the usual moist chamber. After three hours they 

 were examined, the cover-glass with the drop being lifted off and 

 allowed to fall on (1) a drop of acetic-iodine-green,J or (2) a droj) of 

 picro-carmine. After a few minutes dilute glycerin is run under the 

 cover. Both yield excellent results. The nuclei in the tubes are 

 thus more deeply stained than the cytoplasm. 



Longitudinal sections of the stigmas serve for the study of the 

 entrance of the pollen- tubes. The author used alcoholic material, 

 without any staining, mounted in glycerin. 



The pollen-tubes in the conducting tissue may be studied either 

 in longitudinal sections of the stylo, or by laying open the style, and 

 drawing a needle through the canal, thus dragging out tho conducting 

 tissue. In the latter case care must be taken to tangle tho strands as 

 little as possible, and methyl-blue should bo used as a stain, other- 

 wise the transparency of the pollen-tubes renders them very difficult 

 to follow. The very greatly elongated cells of the conducting tissue 

 are almost exactly the diameter of the p(dlen-tubes, and are liable to 



♦ Bot. Gazette, x. (1885) pp. .353-4. f Sec this Journal, supra, p. 1028. 



J A drop of 1 per cent. a<"ctic acid, to wliich a hiquU drop of iodiiic-grocn is 

 iylded. (Htrasburgor, ' Noue Unturauchuiigoii,' p. G.; 



