Practical physiology of plants / by Francis Darwin and E. Hamilton Acton.

  • Darwin, Francis, Sir, 1848-1925.
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: Practical physiology of plants / by Francis Darwin and E. Hamilton Acton. Source: Wellcome Collection.

    43/354 (page 19)
    CH. Il] IODINE METHOD. cover them\ The solution is now coloured by the addition of a little tincture of iodine, and is ready for use. Delicate leaves, such as those of submerged water- plants, when placed in Schimper's solution, are rendered so transparent that every detail of starch-distribution can be studied under the microscope in the leaf examined as a transparent object. (26) Variegated leaves. Test Sachs' method on a variegated leaf such as that of the ivy or of Arundo donax. In the case of the ivy a rough plan of the green and white parts of the leaf must be traced on paper placed under the leaf, which may best be done by a broken line made with a blunt instru- ment dotted along the lines separating the chlorotic from the green parts of the leaf The iodine-stained leaf is then compared with the plan. With Arundo no such process is necessary, the chlorotic regions are in longi- tudinal stripes, and it is only necessary to cut out of the leaf a short piece, which, after staining in iodine, can be replaced between the base and apex of the leaf to which it belonged: the colourless stripes in the fresh part corre- spond to yellow stripes in the stained part, and the purple to the green. Twelve hours is necessary for extracting the chlorophyll, and an hour for iodine staining. (27) Disappearance of starch in darkness. Either of the methods may be tried on submerged water-plants (e.g. Elodea, Potamogeton) which have been * Chloral hydrate 8 parts, water 5 parts. 2—2