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

  • Hermann Schacht
Date:
1855
Catalogue details

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.

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    division of tlie pollen-cell into two unequal halves takes place in the round pollen-grain. Here also that one of the derivative cells which lies opposite to the fissure in the cuticle is much smaller than the other. The smaller of these cells, however, does not, as in Lai'ix, Finns, Picea, and Abies, become developed into the cellular body which is nourished by the larger derivative cell of the jiollen-grain. The smaller cell undergoes no further change ; the larger cell, on the other hand, becomes the pollen- tube, which breaks through the now-softened gelatinous mem- brane of the true pollen-cell, whereby the cuticle,.as in Larix, is striiipcd off in the form of a two-flai)ped covering. In these plants those pollen-tubes which have penetrated into the nucleus of the ovule always have their cuticle stripped oft’; they ter- minate on their free side with the small undeveloped derivative cell (Thuja, Juniperus, Taxus). In Cupressus the pollen-grains not unfrequeutly protrude tubes, whilst still in the pollen-sacs; in these free tubes a cell-formation by division frequently takes place. 3. The scale which carries the pollen-sacs of the above-named Coniferse (which pollen-sacs have frequently been taken for the true anthers) is shown by following out the developement to be the true anther of these plants. The pollen-sacs are developed by a peculiar formation of leaf-tissue at certain parts of these anthers, such part in Thuja, Cupressus, Callitris, and Juniperus communis, being the underside of the stalk. In Taxus, on the other hand, the pollen-sacs appear in the form of five or six loculi on the inner side around the stem of the shield-like anthers; they open like the others by a fissure. The ])ollen-sacs of the Cycadete also are certainly not to be regarded as real anthers, but as those parts of the anther which perfect the pollen ; the scale which bears this pollen-sac is the true anther. The male blossom (the catkin) of the Coniferae and CycadesB consists therefoi'e of a stem-like portion, the axis, upon which a congeries of leaves arc perfected as anthers; it is to be regarded as a single blossom, whilst the male catkins of the Amentaceaj really have distinct flowers. 4. In Podocaiqms the construction of the anther is similar to that in the Abietina?; it is bilocular; the loculi are situated