ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 75 



the synthesis of proteids out of nitrates and sugar in the leaves of Heli- 

 anthus annuus ; this can take place in the dark. 



Fermentation without Cells. * — F. B. Ahrens finds that yeast ex- 

 tract may be concentrated by cooling to a temperature not lower than 

 — 2°, stirring and expressing the liquor from the resulting magma of 

 crystals. By repeating this process several times the specific gravity of 

 the liquor may be raised from 1-0378 at 12° to 1-0765 at 14°. This 

 concentrated extract gave satisfactory results on experiments where the 

 original extract was too dilute. The author considers that zymase is 

 present as a colloidal substance and not in a state of true solution ; that 

 its loss of activity is due to acidity which always develops in a few hours, 

 and that the fluorescence which disappears when the extract is kept or 

 used as a fermenting agent is caused by the zymase itself. 



New Mode of Measuring Transpiration, f — L. Buscalioni and G. 

 Pollacci utilise for this purpose the property of an alcohol-ether solution 

 of collodion to become turbid in contact with aqueous vapour. By this 

 means they determined that, in a large number of plants, transpiration is 

 less energetic from the red than from the green plants. 



y. General. 



Limits of Variation in Plants. X — Dr. J. W. Harshberger describes 

 and tabulates the results of a long series of observations on the variabi- 

 lity of the following organs : — Fruit of Podophyllum peltatum, leaf of 

 Liriodendron tulipifera, leaf of Ampelopsis Veitehii, fruit of Quercus alba 

 and of Q. prinus palustris, leaf of Menispermum canadense, entire plant of 

 Arisxma tripliyllum. leaf of Sanguinaria canadensis, leaf of Ailanthus 

 glandulosa. In three instances (Liriodendron tulipifera, Sanguinaria 

 canadensis, Ailanthus glandulosa) it was found that variation in the size 

 and shape of the leaves is in part due to the persistence of juvenile forms, 

 to the arrested development of such leaves, and to their evolution and 

 transformation into higher forms. These changes are in most cases due 

 to two causes, — the internal hereditary impulse and the direct environ- 

 mental influence. 



Heterogenesis and Evolution. § — S. Korschinsky marshalls a large 

 number of observations on heterogenesis, especially in connection with 

 their bearing on the evolution of species, under the following heads : — 

 Variations in growth ; variations in the stem ; variations in the foliage ; 

 form of the leaves ; colour of the leaves ; colour of the flowers ; variations 

 in the structure of the flower ; variations in the time of blossoming ; 

 variations in the fruit ; the nature of heterogenesis ; the peculiarities of 

 heterogenetic characters ; the external conditions of heterogenesis ; the 

 directions of variability ; the properties of heterogenetic variations ; 

 the heredity of heterogenetic deviations. 



* Zeit. ano;ew. Chem., 1900, pp. 483-6. Sec Journ. Chem. Soc, lxxviii. (1900) 

 Abstr. ii. pp. 610-1. Cf. this Journal, 1899, p. G22. 



t Atti 1st. Bot. Univ. Pavia, vii. (1900) 13 pp. and 1 pi. Sec Bot. Centralbl., 

 lxxxviii. (1901) p. 186. 



X Proc. Acad. Nat. Sci. Philadelphia, liii. (1901) pp. 305-19. 



§ Flora, lxxxix. (1901) Erganzbd., pp. '240-303. 



