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Show ·t) DHOSERA ROTUNDIFOLIA. CHAP. I. part, which alone is capahle of moveme~t, consists of a prolo~gation of the leaf; the spiral vessels bem~ extended from this to the uppermost part. We shall hereafter .see that th~ te~·minal tentacles of the divided leaves of Rondula are still m an intermediate condition. The glands, with the exception of those borne by the extreme FIG. :.1. (D1·osem 1·otundijolia.) Longitudinal section of a gland; greatly magnified. From Dr. Warming. marginal tentacles, are oval, and of nearly uniform size, viz. about 5 t} 0 of an inch in length. Their structure is remarkable, and their functions complex, for they secrete, absorb, and are acted on by various stimulants. They consist of an outer layer of small polygonal cells, containing purple granular matter or fluid, and with the walls thicker than those of the podicels. CIIAP. I. STRUCTURE OF THE LEAVES. 7 Within this layer of cells there is an inner one of differently shaped ones, likewise filled with purple fluid, but of a slightly different tint, and differently affected by chloride of gold. These two layers are sometimes well seen when a gland has been crushed or boiled in caustic potash. According to Dr. V'-l arming, there is still another layer of much more elongated cells, af; shown in the accompanying section (fig. 3) copied from his work; but these cells were not seen by Nitschke, nor by me. In the centre there is a group of elongated, cylindrical cells of unequallongthR, bluntly pointed at their upper ends, truncated or rounded at their lower ends, closely pressed together, and remarkable from being surrounded by a spiral line, which can be separated as a distinct fibre. These latter cells are :filled with limpid fluid, which after long immersion in alcohol deposits n1uch brown matter. I presume that they are actually connected with the spiral vessels which l'Un up the tentacles, for on several occasions the latter were seen to divide iuto two or three excessively thin branches, which could be traced close up to the spiriferous cells. Their development has been described by Dr. Warming. Cells of the same kind have been observed in other plants, as I hear from Dr. Hooker, and vvore seen by me in the margins of the leaves of Pinguicula. WhateYer their function may bo, they are not necessary for the secretion of the digestive fluid, or for absorption, or for the communication of a motor impulse to other parts of the leaf, as we may infer from the structure of the glands in some other genera of the Droseracere. The extreme marginal tentacles differ slightly from the others. Their bases arc broader, and besides their own vessels, they receive a fine branch from those which enter the tentacles on each side. Their glands are much elongated, and lie embedded on the upper surface of the pedicel, instead of standing at the apex. In other respects they do not differ essentially from the oval ones, and in one specimen I found every possible transition between the two states. In another specimen there were no long-headed glands. These marginal tentacles lose their irritability earlier than the others; and when a stimulus is applied to the centre of the leaf, they are excited into action after the others. When cut-off leaves are immersed in water, they alone often become inflected. The purple fluid or granular matter which :fills the cells of the glands differs to a certain extent from that within the cells of the pedicels. For when a leaf is placed in hot water or in certain acids, the glands become quite white and opaque, whereas |