92 ON THE PLANT-CELL. 



are composed of a bright yellow substance (mucus ?), so that the fibres 

 do not altogether appear unlike some Confervce. With respect to the 

 real character of these peculiar formations I have nothing at all to 

 observe. The system of vessels discovered by Gottsche, in Preissia 

 commutata, may be adduced as the only thing at all analogous to them, 

 but just as isolated and mysterious. In this case the individual cells are 

 traversed by similar tubes, which appear to perforate the cell-wall itself. 

 In either case, an elucidation of the mystery can be expected only from 

 tracing the course of development. 



b. In the antheridia of the Characece, Mosses, and Lichens, as well as 

 of the Ferns, the layer of mucus is apparently transformed, in the 

 tender cell, into a spiral filament ; the history of which has, as yet, been 

 by no means rendered clear. Its relation to the soft mucous layer 

 especially, still requires more particular investigation ; and it might also 

 probably be a question for determination, whether the cells in which 

 these spiral filaments are developed are in reality perfect cells or only 

 the nuclei of cells, that is to say, hollow cytoblasts. The best recent 

 researches on the subject are those of Nageli.* 



V. Motion of the Cell Contents. 



40. The fluid contents of vegetable cells exhibit two kinds of 

 motion, as to the causes of which we are still wholly in the dark. 

 In most plants in the families of the Characea, Najadacce, and 

 Hydrocharidacea, there is observable in each cell a single current 

 ascending on the one side and descending on the other, the fluid 

 constituting which, differs in colour, consistence (mucosity), and 

 insolubility in aqueous fluids, from the remainder of the transparent 

 cell-juice. The current is rendered more evident, in some cases, 

 from its carrying along with it the spherical bodies contained in 

 the fluid (starch, chlorophyll, mucus, &c.) ; but for the most part it 

 is sufficiently evident of itself. 



The motion is best seen in the species of Nitella, in the hairs on the 

 roots of Hydrocharis morsus ranee, and in Vallisneria spiralis. Each, 

 however, has its peculiarities. In Nitella the moving stream is very 

 considerable, so that only a narrow streak remains at comparative rest 

 between the ascending and descending currents. The stream is strong 

 and rapid, and carries along with it starch -granules of considerable size. 

 Its course is not exactly parallel to the axis of the cell, but forms a small 

 angle with it. In two contiguous cells the currents flowing on the par- 

 tition between them run in opposite directions, consequently throughout 

 the whole plant the ascending streams are on one side, and, in fact, 

 owing to their oblique direction, form a spiral ; this is the case also with 

 the descending streams. When very young, the cells are perfectly trans- 

 parent, a condition which they subsequently lose, in consequence of 

 numerous granules, covered with chlorophyll, arranging themselves in 

 slender parallel rows upon the walls exactly in the course of the streams, 

 and leaving on each side only the narrow interspace between the streams 



* Schleiden und Nageli, Zeitschrift fiir wissenschaftliche Botanik, Bd. I. Heft. I. 

 S. 168. et seq. This paper is translated by the Ray Society in " Reports and Papers 

 on Botany," 1845. 



