ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 323 



venous colour returned in about the same time. By intense illumination 

 of a single cell or part of a cell a bright-red area formed only about the 

 illuminated spot. 



The development of oxygen in the light and its absorption in the 

 dark can be followed with a spectral ocular, or, better still, with the 

 microspectral photometer. It is then seen that on illuminating the cell 

 (gaslight or an electric incandescent sufhVes) in place of the dark 

 absorption-bands of oxygenless haemoglobin-,' the two dark bands of 

 oxyhemoglobin appear. The change becomes apparent in ten to twenty 

 seconds, and first occurs at the surface of the cells, from which it spreads 

 outwards. Per contra, in the dark the hasmoglobin-band returns. 



The next step was to ascertain if the unequal effects of the different 

 rays of the spectrum upon the development of oxygen could be rendered 

 visible to the naked eye. For this purpose a filament of spirogyra was 

 placed in venous blood under a cover-glass, and illuminated with a 

 spectrum of about 1 cm. long from a Sugg's burner of 50 candle-power. 

 In about fifteen minutes the boundary between the arterial and venous 

 colour was seen in the extreme visible red, and it attained its maximum, 

 about 1 mm., near C. Although, owing to the cloudiness of the weather, 

 the experiments with sunlight were few, they were sufficient to show 

 that the strongly refracting rays were more powerful than those of the 

 gas spectrum. The maximum lay in the middle of the visible red, not 

 in the orange or yellow. The action in the green between D and E was 

 less strong than in the blue-green or blue. Even in the violet a slight 

 action was perceptible. In conclusion, the author remarks that he does 

 not doubt that plants with red, yellow, or brown chlorophyll will give 

 characteristic " hasmatospectrograms " of the development of oxygen. 



Microchemical Tests for Callus.* — Mr. F. W. Oliver gives the fol- 

 lowing microchemical tests for the callus which he finds in the trumpet- 

 hyphse and true sieve-tubes of Mac7-ocystis and Nereocystis ; f but they 

 apply also to the callus in the sieve-tubes of Phanerogams. 



(1) Bussow's callus reagent (a mixture of equal parts of chlorzinc- 

 iodine and iodine in potassic iodide) stains callus a deep brown ; a very 

 delicate test ; (2) Coralline-soda (prepared by adding rosolic acid to a 

 strong aqueous solution of sodium carbonate) gives a brilliant rose-pink ; 

 (3) Bismarck brown dissolved in water reveals a very decided stratifi- 

 cation ; (4) Hoffmann's blue (dissolved in 50 per cent, of alcohol) stains 

 the callus-plates a brilliant blue ; (5) chlorzinc-iodine does not, as a rule, 

 stain the plates, but they swell up and show stratification ; (6) methylene- 

 blue gives negative results; (7) hematoxylin, with dilute solutions, the 

 callus-plates stain deeply; (8) liydric sulphate causes the plates to swell 

 up, showing a very beautiful stratification, and finally they are completely 

 dissolved ; (9) potash causes them to swell up, but does not actually 

 dissolve them. 



Beauregard, H., and V. Galippe. — Guide pratique pour les travaux de 

 Micrographie, comprenant la Technique et les applications du Microscope a 

 l'Histologie vegetale et animale, a la Bacteriologie, a la Clinique, a l'Hygiene 

 et a la Medecine legale. (Practical Guide to Microscopy, including technique 

 and the application of the Microscope to vegetable and animal Histology, to 

 Bacteriology, to Clinics, to Hygiene, and to Medical Jurisprudence.) 



2nd ed., vii. and 901 pp., 586 figs., 8vo, Paris, 1888. 



Aon. of Bot i. (1887) pp. 109-11. t See ante, p. 265. 



