III. On the continuity of the protoplasm through the walls of vegetables cells

Abstract

After quoting a passage from Professor Sachs’ “ Vorlesungen fiber Pflanzen-Physiologie,” “every plant however highly organised is fundamentally a protoplasmic body forming a connected whole, which, as it grows on, is externally clothed by a cell membrane and internally traversed by innumerable transverse and longitudinal walls,’ the author suggests that any observations which demonstrate an actual continuity in organs of large extent must be of interest, as tending to show the truth of Sachs’ statement in a sense somewhat more literal than his own. At the time that the above remarks were written, the instances of the existence of any protoplasmic continuity between adjacent cells were but few, being limited to sieve tubes and to Tangl’s results with regard to the endosperm cells of Strychnos, Phœnix, and Areca. Then came the author’s investigations upon the pulvini of Mimosa, Robinia, and Amicia, and subsequently to them, but previous to the present communication, appeared an important paper by Russow, in which he had proved that in the bast parenchyma cells and the phloem ray cells of numerous plants, e.g ., Populus Salix, &c., the closing membranes of the pits were perforated by fine protoplasmic threads. In the present paper the author details his results upon pulvini, treats of the methods employed, and gives an account of his investigations' as to the structure of endosperm cells which were undertaken with the object of controlling his previous researches. Since experiments showed that all preservative reagents were unsatisfactory, fresh material alone was employed. In investigating the subject of protoplasmic continuity the method of swelling the cell-wall and subsequent staining was adopted. Either sulphuric acid or chlor. zinc. iod. was used as the swelling agent; and, after washing, the sections were stained with Hoffmann’s violet—in which case they were subsequently washed out with glycerine—or with Hoffmann’s blue. The latter dye was found to be a particularly satisfactory reagent for staining the protoplasm alone, while methylene blue, on the other hand, especially stains the cell-wall. After the action of chlor. zinc. iod. and subsequent staining it was still found to be impossible to colour the protoplasmic threads running through the cell-wall, and since the author’s experiments had led him to believe that this was merely due to phenomena of diffusion (the solution of the colloidal dyes diffusing but little into the colloidal protoplasm), he adopted the modification of dissolving the solid Hoffmann’s blue in a 50 per cent, solution of alcohol saturated with picric acid, which was found to be perfectly successful as a stain.