Page:Insectivorous Plants, Darwin, 1899.djvu/53

CHAPTER III.

AGGREGATION OF THE PROTOPLASM WITHIN THE CELLS OF THE TENTACLES.

Nature of the contents of the cells before aggregation―Various causes which excite aggregation―The process commences within the glands and travels down the tentacles―Description of the aggregated masses and of their spontaneous movements―Currents of protoplasm along the walls of the cells―Action of carbonate of ammonia―The granules in the protoplasm which flows along the walls coalesce with the central masses―Minuteness of the quantity of carbonate of ammonia causing aggregation―Action of other salts of ammonia―Of other substances, organic fluids, &c.―Of water―Of heat―Redissolution of the aggregated masses―Proximate causes of the aggregation of the protoplasm―Summary and concluding remarks―Supplementary observations on aggregation in the roots of plants.

I will here interrupt my account of the movements of the leaves, and describe the phenomenon of aggregation, to which subject I have already alluded. If the tentacles of a young, yet fully matured leaf, that has never been excited or become inflected, be examined, the cells forming the pedicels are seen to be filled with homogeneous, purple fluid.^[1] The walls are lined by a layer of colourless, circultfting protoplasm ;^[2] but this can be seen with much greater distinctness after the process of aggregation has been partly effected than before. The purple fluid which exudes from a crushed tentacle is somewhat coherent, and does not mingle with the surrounding water; it contains much flocculent or granular matter. But

this matter may have been generated by the cells having been

1. [The statement as the absence of nucleus in the stalkcells of Drosera (Francis Darwin, 'Quaterly Journal of Microscopical Science.' 1876) has been shown by Pfeffer to be quite erroneous ('Osmotische Untersuchungen.' 1877, p. 197).―F. D.]
2. [Mr. W. Gardiner ('Proc. R. Soc.' No. 240, 1886) has described a remarkable body nameds by him the "rhabdold," which exists within the epidermic cells of the stalk of the tentacles. This body was discovered in Dorsera dichotoma, but exists also in D. rotundifolia: in the former species, in which it has been more or less spindle-shaped mass, stretching diagonally across the cell, the two ends being embedded in the cell-protoplasm. "It is present in all leaf except the gland cells and the cells immediately beneath the same." Further reference to the rhabdoid will be found at p. 35.―F. D.]