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

  • Hermann Schacht
Date:
1855
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Licence: Public Domain Mark

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

    169/230 (page 145)
    mode of pi-oceeding can be given for tracing the developement of the ovule, which must be regulated by the number and airange- ment of the ovules in the ovaiy. Sometimes the transverse Section, sometimes the longitudinal, will be most serviceable. The first appearance of the nucleus of the ovule out of the tissixe of the placenta in the form of a conical cellular little excrescence, the origin of the coatings of the ovule in the shape of circular enveloping folds around the nucleus, the slight con- temporaneous bending of the ovule, and the a])pearance and natiu’e of the embiyo-sac within the ovule, must all be noticed. In Hippuris and INIyriophyllum, the ovides are without in- teguments, and are anatropal. They are also provided with a vascular bundle in the naked nucleus. In Thesium, the nucleus is also naked, but has no vascular bundles. As spe- cimens of plants, the ovules of which are pi’ovided with inte- guments, may be mentioned Jxiglans, Taxus (in which the ovule is orthotropal), Impatiens, and the Rhinanthaceae. In the latter, the ovule is anatropal, and the embryo-sac is ex- tended into sac-shaped prolongations, which lie in the paren- chyma of the integument. In Hych'ocharis and Polygonum, Viola, OEnothera, and the Orchideae, the ovules have two inte- guments. In Polygonum, the ovule is orthotropal, and in the Orchideae, anati-opal. The ovules of many plants at the period of flowering are so large that they may be detached, placed upon the finger, and sections made of them; the direction of the cut must be parti- cularly attended to. One side of the ovule must first be removed with an excessively sharp hollow-sided razor; the oxuile must then be carefully turned round with a fine camel’s-hair brush, and the other side removed in like manner by passing the razor steadily and slowly through the ovule, so that of the whole ovule there will remain only the middle lamella. The object must not be permitted to become dry during the process of cutting, and conse- quently the finger must be kept moist. The lamella, thus prepared, must be immediately placed under the microscope ^vithout a covering-glass. It will freqxiently happen that the section may be improved by a third or a fourth cut, made in the same manner; and although, in doing this, the object is sometinxes spoiled, o