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Show 310 DION lEA 1\:fUSCIPULA. CHAP. XIII. meat for eleven days, a third leaf for eight days, and a fourth (but this had been cracked ~nd injured) for only six days. Bits of cheese, or case1n, were placed at one end and albumen at the other end of three leaves; and the ends with the former opened after six, eight, and nine days, whilst the opposite ends opened a little later. None of the above bits of moat, albu1nen, &c., exceeded a cube of T 1o of an inch (2·54 1nm.) in size, and were sometimes smaller; yet these small portions sufficed to keep the leaves closed for many days. Dr. Canby informs me that leaves re1nain shut for a longer ti1ne over insects than over meat; and from what I have seen, I can well believe that this is the case, especially if the insects are large. In all the above cases, and in many others in ·which leaves remained closed for a long but unknown period over insects naturally caught, they were more or less torpid when they reopened. Generally they were so torpid during many succeeding days that no excitement of the filaments caused the least movement. In one instance, however, on the day after a leaf opened which had clasped a fly, it closed vYith extreme slowness ·when one of its fila1nents was touched; and although no object was left enclosed, it was so torpid that it did not re-open for the second time until 44 hrs. had elapsed. In a second case, a leaf which had expanded after re1naining closed for at least nine days over a fly, when greatly irritated, moved one alone of its two lobes, and retained this unusual position for the next two days. A third case offers the strongest exception which I have observed; a leaf, after remaining clasped for an unknown time over a fly, opened, and when one of its filaments was touched, closed, though rather slowly. Dr. Canby, CHAP. XIII. MANNER OF CAPTURING INSECTS. 311 who observed in the United States a large number of plants which, although not in their native site, were probably more vigorous than my plants, informs .me that he has" several times known vigorous leaves to devour their prey several ti1nes; but ordinarily twice, or, quite often, once was enough to render them unserviceable." Mrs. Treat, who cultivated many plants in New Jersey, also informs me that "several leaves caught successively three insects each, but most of them were not able to digest the third f:1. y, but died in the attempt. Five leaves, however, digested each three flies, and closed over the fourth, but died soon after the fourth capture. Many leaves did not digest even one large insect." It thus appears that the power of digestion is so mew hat limited, and it is certain that leaves always remain clasped for many days over an insect, and do not recover their power of closing again for many subsequent days. In this respect Dionrea differs from Drosera, which catches and digests many insects after shorter intervals of time. We are now prepared to understand the use of the marginal spikes, which form so conspicuous a feature in the appearance of the plant (fig. 12, p. 287), and which at first seemed to me in my ignorance useless appendages. From the inward curvature of the lobes as they approach each other, the tips of the marginal spikes first intercross, and ultimately their bases. Until the edges of the lobes come into contact, elongated spaces between the spikes, varying from the -A, to the Yo- of an inch (1·693 to 2·54 mm.) in breadth, according to the size of the leaf, are left open. Thus an insect, if its body is not thicker than these measurements, can easily escape between the crossed spikes, when disturbed by the closing lobes and in- |