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.

    214/230 (page 190)
    polleu-tube of Pinus, by division of one motber-cell. I Lave frequently been fortunate enougb, whilst the pollen-tube was lying over a corpusculum, to detach it in an uninjured state, so that I could fully and accurately examine the cellular body whilst within the pollen-tube. The apex, or x'ather the extension of the bladder-like pollen-tube in which the above-mentioned cellular body lies, penetrates into the corpusculum, and becoming distended, fills up by degrees the hollow of the latter. The cellular body then becomes enlarged by repeated, but xxot always regular, division, so that the number and arrangement of the cells is not always the same. The corpuscula of one and the same embryo-sac difier also amongst them.seh'es in size and shape. I have succeeded in completely detaching, at different periods of developement, that portion of the pollen-tube which has penetrated into the corpusculum. Generally, however, the pollen-tube breaks off at the place where it passed the mouth of the corpusculum. The embryonal tubes are formed out of the upper layers of cells, which latter are formed within the cor- pusculum out of the cellular body existing in the pollen-tube before the entrance of the latter into the corpusculum. The rudiment of the embryo, on the other hand, originates from the lower layers of cells. By the growth lengthwise of the em- bryonal-tubes the rudiment of the embryo is (as in Pinus) carried downwards into the wedge-shaped loosened portion of the albumen which is situated beneath the cor])uscula, and there proceeds to develope itself into the embryo. The corpuscula and the embryonal tubes dry up as soon as their office has been fulfilled ; the same is the case in Pinus. In Taxus the pollen-tube really becomes enlarged in the interior of the corpusculum, as Schleiden has already noticed ; tills, however, does not occur in Pinus. In Pinus the po.sition of the corpuscula of the impregnated ovule is such that their apices turn upwards ; the cone hangs downwards, so that the ovules have their micro])yles directed upwards. In this case, tliereforc, the cellular body, or the four-celled embryonic vesicle, cixn sink downwards by gravitation ; in Taxus, where the apex of the corpusculum of the impregnated ovule points downwards, the change of place of the embryonic vesicle could not be