. The cytoplasm of the plant cell. Plant cells and tissues; Protoplasm. the longitudinal axis, while the small vacuoles are accumulated against the proximal wall of the cell (Mangenot). This polarity of arrangement, which becomes more marked as digestion becomes more active, clearly indicates that these cells are traversed by a continuous flow of material caused by protein digestion (proteolesis) at the level of the extremities of the tentacles. Thus, the "aggregated" state of the vacuoles, , their irregular dis- position, seems to correspond to differ- ing physiological conditio
. The cytoplasm of the plant cell. Plant cells and tissues; Protoplasm. the longitudinal axis, while the small vacuoles are accumulated against the proximal wall of the cell (Mangenot). This polarity of arrangement, which becomes more marked as digestion becomes more active, clearly indicates that these cells are traversed by a continuous flow of material caused by protein digestion (proteolesis) at the level of the extremities of the tentacles. Thus, the "aggregated" state of the vacuoles, , their irregular dis- position, seems to correspond to differ- ing physiological conditions—to a secre- tion in the cells which cover the ex- tremity of the tentacle, to an absorp- tion in the cells of the stalk—but both these processes indicate the passage of a current across the cells. This same arrangement of vacuoles is found in young sieve tubes in the angiosperms in which the fragmented and polarized vacuoles are very polymorphic. In these cells, large vacuoles and small filamen- tous or reticulate vacuoles are found. They are also found in the conducting elements of the Laminariales and the Rhodophyceae (Mangenot) (Fig. 123). Recent work seems to suggest that the vacuoles undergo a similar frag- mentation each time that the cells are in the process of active secretion (Man- genot, Mile. Py, Thomas, Guillier- mond). The reason for this is not yet known. Another phenomenon to consider here is that of the frequent changes in form of vacuoles in many cells. The observation of a species of Saprolegnia in van Tieghem and Le Monnier cells, grown in a nutrient solution to which neutral red has been added, made it possible to record this phenomenon under excellent conditions (Fig. 120). In the extremities of growing filaments the vacuoles generally appear as very small elements shaped as granules, rods or filaments. These ele- ments are carried along by cytoplasmic currants which cause them to change shape constantly. They are capable of swelling and of contracti
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Keywords: ., bookcentury1900, bookcollection, booksubjectplantcellsandtissues
