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Show 346 GLANDULAR HAIRS, CIIAP. XV. which minute Diptera are sometimes, though not often, caught.* The cells of the glands contain bright pink fluid, charged with granules or with globular masses ?f pinkish pulpy matter. This matter must be protoplasm, for 1t 1s seen to undergo slow but incessant changes of form if a gland be placed in a drop of water and examined. Similar movements were observed after o·lands had been immersed in water for 1, 3, 5, 18, and 27 hrs. Even after this latter period the glands retained their brjght pink colour; and the protoplasm within their cells d~d not appear to have become more aggregated. The contmually changing forms of the little masses of prot~plasm are not due to the absorption of water, as they were seen 1n glands kept dry. A flower-stem, still attached to a plant, was bent (May 29) so as to remain immersed for 23 hrs. 30 m. in a strong infusion of raw meat. The colour of tbe contents of the glands was slightly changed, being now of a duller and more purple tint than before. The contents also appeared more aggregated, for the spaces between the little masses of protoplasm wero wider ; but this latter result did not follow in some other and similar experiments. The masses seemed to change their forms more rapidly than did those in water; so that the cells had a djfferent appearance every four or five minutes. Elongated masses became in the course of one or two minutes spherical; and spherical ones drew themselves out and united with others. Minute masses rapidly increased in size, and three distinct ones were seen to unite. The movements were, in short, exactly like those described in the case of Drosera. The cells of the pedicels were not affected by the infusion ; nor were they in the following experiment. Another flower-stem was placed in the same manner and for the same length of time in a solution of one part of nitrate of ammonia to 146 of water (or 3 grs. to 1 oz.), and the glands were discoloured in exactly the same manner as by the infusion of raw meat. . Another flower-stem was immersed, as before, in a solution of one part of carbonate of ammonia to 109 of water. The glands, after 1 hr. 30 m., were not discoloured> but after 3 hrs. 45 m. most of them had become dull purple, some of them blackish- --------- -- * In the case of Saxifraga tridar. tylites, Mr. Druce says (' Phtn·maceutical ,Journal,' May 1~75 ) that he examined some dozens of plants, and in almo!:lt every in-stnnce remnants of insects ad· ll ered to the lf'a ves. So it is, as I h ar from a friend, with this plant in Ireland. CHAP. xv. THEIR POWER OF ABSORPTION. 347 green, a few being still unaffecte~. The little m~,sses of protoplasm within the cells were seen 1n movement. l he cells of the pedicels were unaltered. The experiment was repeated, and a fresh flower-stem was left for 23 hrs. in the solution, and now a great effect was produced; all the .gl~nds were much black~ned, and the previously transparent flu1d 1n the cells of the pediCels, even do\vn to their bases, contained spherical masses of granular matter. By comparing many different hairs, it was evident that the glands first absorb the carbonate, and that the effect thus produced travels down the hairs from cell to cell. The first change which could be observed is a cloudy appearance in the fluid, due to the formation of very fine granules, which afterwards aggregate into larger masses. Altogether, in the darkening of the glands, and in the process of aggregation •travelling down the cells of the pedicels, there is the closest resemblance to what takes place when a tentacle of Drosera is immersed in a weak solution of the same salt. The glands, however, absorb very much more slowly than those of Drosera. Besides the glandular hairs, there are star-shaped organs which do not appear to secrete, and which were not in the least affected by the above solutions. Although in the case of uninjured flower-stems and leaves the carbonate seems to be absorbed only by the glands, yet it enters a cut surface much more quickly than a gland. Strips of the rind of a flower-stem were torn off, and the cells of the pedicels were seen to contain only colourless transparent fluic1; those of the glands including as usual some granular matter. 'rhese strips were then immersed in the same solution as before (one part of the carbonate to 109 of water), and in a few minutes granular matter appeared in the lower cells of all the pedicels. The action invariably commenced (for I tried the experiment repeatedly) in the lowest cells, and therefore close to the torn surface, and then gradually travelled up the hairs until it reached the glands, in a reversed direction to what occurs in uninjured specimens. The glands then became discoloured, and the previously contained granular matter was aggregated into larger masses. Two short bits of a flower-stem were also left for 2 hrs. 40 m. in a weaker solution of one part of the carbonate to 218 of water; and in ·both specimens the 'pedicels of the hairs near the cut ends now contained much granular matter; and the glands were completely discoloured. Lastly, bits of meat were placed on some glands; these were examined after 23 hrs., as were others, which had apparently not long before caught minute flies; but they did not present any |