Handbook of practical botany : for the botanical laboratory and private student / by E. Strasburger ; edited from the German by W. Hillhouse ; revised by the author, and with many additional notes by author and editor.

  • Strasburger, Eduard, 1844-1912.
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: Handbook of practical botany : for the botanical laboratory and private student / by E. Strasburger ; edited from the German by W. Hillhouse ; revised by the author, and with many additional notes by author and editor. Source: Wellcome Collection.

    86/514 (page 55)
    therefore, provided they correspond with the radii, show the cells in longitudinal view, while tangential sections, which cut the radii at right angles, show cross-sections of the cells. Chlorzinc iodine solution colours the thickening layers very beautifully violet. By slower swelling usually numerous lamellae are brought into sight. We turn now to the pine wood [Finns, etc., any species, prefer- ably F. sylvestris, the Scotch fir], in order to learn to know bordered pits. For this purpose we take a piece of wood, either dry, or, better still, preserved in alcohol, from a stem as old as possible. First we prepare with a sharp pocket-knife the suitable surfaces for cutting—one radial, parallel to the long axis of the stem, one tangential tO' the same, and one directed perpendicularly to this axis. The concentric yearly rings which are visible with the naked eye upon every piece of pine wood will provide us with the necessary bases from which to get information as to the direc- tions in question.. The radial longitudinal section cuts the yearly rings perpendicularly. The tangential longitudinal section is so much the more perfect, the more parallel it runs to the yearly rings. The cross-section is directed perpendicularly to both longi- tudinal sections. In the following preparation of microscopical sections, in order that the sections shall be good, and not to damage the razor, quite special precautionary rules must be adopted. If the razor is ho-llow-ground, rightly directed sections can be taken only from the edges of the piece of wood, i.e., so long as the back of the razor does not yet rest upon the cut surface. However, in general, only slightly hollowed razors should be used for cutting wood, as those greatly hollowed easily “ give.” It is recommended to use razors which are ground flat on one side, i.e., the side which will rest upon the cut surface; but these razors have the disad- vantage that they are not easily sharpened. The cut surface must always be moistened; the sections must be as thin as possible. It is not necessary to have them of any particular size. A section which appears to be too thick should not be cut to the end ; it is better to withdraw the razor from the cut in order not to notch the edge. The razor must be sharp, otherwise it will tear the cell- walls, and separate the inner thickening layers from the outer. The wood preserved in alcohol cuts more easily than Avhen dry, especially when the former has been laid subsequently in a mixture of equal parts glycerine and alcohol. The surface of the cut surface prepared by the pocket-knife, as it contains the torn cell-