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Show 352 GLANDULAR HAIRS, CHAP. XV. in amount; but one such mass retained exac~ly the same form as before after an interval of 5 hrs., so that 1t could hardly have consisted of living protopl as~. These. glands seem to have very little or no power of absorptiOn, certainly much less than those of the foregoing plants. Mirabilis longiflora.-The stems and both surfaceR of the leaves bear viscid hairs. Young plants, from 12 to 18 inches in height in my greenhouse, caught so ~any minute Diptera, Coleoptera, and larvre, that they were qt:Ite dusted w~th them. The hairs are short, of unequal lengths, formed of a smgle row of cells, surmounted by an enlarged cell which secretes viscid matter. These terminal cells or glands eontain granules and often globules of granul ar matter. Within a gland which had cauo·ht a small insect, one such mass was observed to undergo ince~sant changes of form, with the occasional appearance of vacuoles. But I do not believe that this protoplasm had been generated by matter absorbed ~ro1n the dead insect; for, on comparing several glands which had and had not caught insects, not a shade of difference could be perceived between them, and they all contained fine granular matter. A piece of leaf was immersed for 24 hrs. in a solution of one part of car· bonate of ammonia to 218 of water, but the hairs seemed very little affected by it, excepting that perhaps the glands were rendered rather more opaque. In the leaf itself, however, the grains of chlorophy 11 near the cut surfaces had run together, or become aggregated. Nor were the glands on another leaf, after an immersion for 24 lll's. in an infusion of raw meat, in the least affected ; but the protopla. m lining the cells of the pedicels had shrunk greatly from the walls. This latter effect may have been due to exosmose, as the infusion was strong. vVe may, themfore, conclude that the glands of this plant either have no power of absorption or that tho protoplasm which they contain is not acted on by a solution of carbonate of ammonia (and this seems scarcely credible) or by an infusion of meat. , N~cotiana tabacum.-This plant is covered with innumerable hairs of unequal lengths, which catch many minute insects. The pedicels of the hairs are di videcl by transverse partitions, and the secreting glands are formed of many cells, containing greenish matter with lit tle globules of some substance. Leaves were left in an infusion of raw meat and in water for 26 hrs., but presented no difference. Some of these same leaves were then left for above 2 Ius. in a solution of carbonate of ammonia, but no effect was produced. I regret that other experiments were not tried with more care, as M. Scbloesing CHAP. XV. THEIR POWER OF ABSORPTION. 353 has shown* that tobacco plants supplied with the vapour of carbonate of ammonia yield on analysis a greater amount of nitrogen than other plants not thus treated; andJ from what we have seen, it is probable that some of the vapour may be absorbed by the glandular hairs. Summary of the Observations on Glandular Hairs.From the foregoing observations, few as they are, we see that the glands of two species of Saxifraga, of a Primula and Pelargonium, have the power of rapid absorption; whereas the glands of an Erica, Mirabilis, and Nicotiana, either have no such power, or the contents of the cells are not affected by the fluids employed, namely a solution of carbonate of ammonia and an infusion of raw meat. As the glands of the Mirabilis contain protoplasm, which did not become aggregated from exposure to the fluids just named, though the contents of the cells in the blade of the leaf were greatly affected by carbonate of ammonia, we may infer that they cannot absorb. We may further infer that the innumerable insects caught by this plant are of no more service to it than are those which adhere to the deciduous and sticky scales of the leaf-buds of the horse-chestnut. The most interesting case for us is that of the two species of Saxifraga, as this genus is distantly allied to Drosera. Their glands absorb matter from an infusion of raw meat, from solutions of the nitrate and carbonate of ammonia, and apparently from decayed insects. This was shown by the changed dull purple colour of the protoplasm within the cells of the glands, by its state of aggregation, and apparently by its more rapid spontaneous movements. . *.' CoJ?ptes rend us,' June 15, 1874. A good abstract of this paper 1s g1ven m the' Gardener's Chronicle,' July 11., 1874. 2 A |