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Show 2 DROSERA ROTUNDIFOLIA. CnAP. I. o·athered by chance a dozen plants, bearing fifty-six fully expanded leaves, and on thirty-one of these dead insects or rmnnants of them adhered ; and, no doubt, 1nany 111ore would have been caught afterwards by th se same leaves, and still more by those as yet not e~panded. On one plant ail six l aves had caught then prey; and on several pla?-ts very many leaves had cauo·ht 1nore than a single Ins ct. On one large leaf I f~und the remains of thirteen distinct insects. }..,lies (l)iptera) are captured much oftener than other insects. The largest kind which I have seen caught was a small butterfly ( Omnonyn~pha pamphilus) ; hut the Rev. H. M. Wilkinson informs me that he found a laro·e living dragon-fly with its body firmly held by tw~ leaves. As this plant is extre1nely common in son1e districts, the number of insects thus annually slaughtered 1nust be prodigious. Many plants cause the death of insects, for instance the sticky buds of the horse-chestnut ( .!Esculus hippocastanum ), without thereby receiving, as far as we can perceive, any aclYnntage; but it was soon evident that Drosera was 'rhich was published in tho Garclcnor's Chronicle,' 1863, p. 30. Mr. Scott shows that gentle initation of tho hairs, as well as insects placed on tho disc of tho leaf, eause the hairs to bond inwar( ls. Mr. A. W. Bennett al o gave anoth('r interesting account of the movements of the loaves before the British Association for l 873. In this amo year Dr. 'Varming publi. hod ::m esf:iay, in which he d.csoriuos tho structure of the so-called hairs, ontitleu, " Sur la Difference entre los 'l'riohomes," &c., extracted. from the proceedings of the Soc. d' 1 list. Nat. de Oopenhague. I shall also have occasion hereafter to refer to a paper by Mr ·. Treat, of N w J erscy, on some American . pccies of Dro ·era. Dr. Burdon Sanderson doli vorod a lecture on Dionroa, before tho Hoyallnstitution (puulish din' Nature,' J uuo 14, 1>::>74), in which a short account of my obsorvn.tiouH on the power of true digestion pos. ·ossed by Drosora anu Dionrca fir.'t appeared. Prof. Al-:lu, Gray has dmLO good service uy calling attention to Drosom, and to other plants having similar hn.hitH, in' Tho Nation ' (1874, pp. ~G l ::m<l ~3 2) , and iu other puulication. . Dr. Hooker, al::;o, in his important n.duross on Camivorous Plant ·(Brit.Assoc.,Bclfast, 1874), has given a history of the subject. CI-IAP. I. STRUCTURE OF THE LEA YES. 3 excellently adapted for the special purpose of catching insects, so that the subject seemed well worthy of jnvestigation. The results have proved highly re1narkable; the n1ore important ones being-firstly, the extraorclinary FIG. 1.* ( Drosem rotundifolict.) Leaf viewed from above; enlarged four time.~;. sensitiveness of the glands to slight pressure au(l to minute doses of certain nitrogenous fluids, as shown by the moven1ents of the so-called hairs or tentacles; * ~1 he drawings of Drosera and Dionma, given in this work, were made tor me by my son George Darwin; those of Aldrovanda, and of the several species of Utri-cularia, by my !:!On Francil:5. 'l'hey have been excellently reproduced on wood by Mr. Cooper, 188 Strand. B 2 |
