The microscope : and its application to vegetable anatomy and physiology / by Dr. Hermann Schacht ; edited by Frederick Currey, M. A.

Hermann Schacht

Date:: 1855

Credit: The microscope : and its application to vegetable anatomy and physiology / by Dr. Hermann Schacht ; edited by Frederick Currey, M. A. Source: Wellcome Collection.

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$rately investigated; tlie deeper tliey lie the more fully deve- loped tliey will be found to be, both in length and breadth, and in the degree of their thickening; they are younger and less de- veloped in ])roportion as they are nearer to the apex. If a section of this nature is treated with iodine and sulpluiric acid, the lower parts of it immediately become blue; towards the apex this change of colour takes place cpiite gi’adually, and passes through the most various shades of yellow, and through red and violet, to blue. The conical end of the stem frequently does not turn blue for many hours, but it becomes rose-i’ed on the application of sugar and sul])huric acid. Beneath this conical ])rotuberance, which may be called the terminal bud, or Punctum vegetationis, and on both sides of it, if the section be well made, are to be seen other small protu- berances, which ai'e coA-ered with the same delicate epidermis as the Punctum vegetationis, and which con.sist of cells of the same nature as those forming the tissue of the Punctum A’ege- tationis. These small protube}’ances appear to be more deve- loped in proportion as they are situated loAver down upon the stem; they may easily be seen to be the rudiments of leaves. Shortly after the appearance of these laidiments of leaves, and in fact in their axils, a similar wart-like protidjerance is often l^roduced, which becomes an axillary bud. The leaf is generally developed withoiit delay; its axillary bud, on the other hand, remains at rest for a time, and then becomes develojied into a branch or a leaf. The apex of the leaf ahvays dies first; it often becomes developed into a mucro. In dicotyledonous })lants, whilst the mid-rib and veins continue to be developed, the edge of the leaf ceases to form neAv cells; the edge thus becomes dentate, serrate, &c. The ju’incipal veins proceed fiom the mid-rib ; the secondaiy and inferior veins, which do not extend to the edge of the leaf, then make their appearance in succes- sion. AVhen the foxnidatioji of all the impoidant parts of the surface of the leaf has been laid, it begins to grow, apparently with tolerable regularity, by cell-extension. .Por tracing the dei^elopement of leaves, young buds should be chosen, and the young leaves removed one by one \mtil the PTinctum A^egeta- tionis is reached, and the latter must then be brought imder$