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Show 320 DION lEA MUSCIPULA. CHAP. XIII. must have been equally affected; and I can understand the divergence of the lobes only by supposing that the cells on the lower side, owing to their state of tension, acted mechanically and thus suddenly drew the lobes a little a part, as soon as the cells on the upper surface were killed and l~s~ their con~ractile power. We have seen that bo1hng water 1n like rnanner causes the tentacles of Drosera to curve backwards ; and this is an analogous movement to the divergence of the lobes· of Dionrea. In some concluding remarks in the fifteenth chapter on the Droseracere, the different kinds of irritability possessed by the several genera, and the different manner in which they capture insects, will be compared. CHAP. XIV. ALDROV ANDA VESICULOSA. .321 CI-IAPTER XIV. ALDROV ANDA VESICULOSA. Captures crustaceans- Structure of the leaves in comparison with those of Dionrea- Absorption by the glands, by tho quadrifid processes, and points on the infolded margins- Aldrovanda vesiculosa, var. auiitralis- Captures prey- Absorption of animal matter. Aldrovanda vesicul(}Sa, var. verticillata- Concluding remarks. THIS plant may be called a miniature aquatic Dionrea. Stein discovered in 1873 that the bilobed leaves, which are generally found closed in Europe, open under a sufficiently high temperature, and, when touched, suddenly clos.e. * They re-expand in from 24 to 36 hrs .. , but only, as it appears, when inorganic objects are enclosed. The leaves sometimes contain bubbles of air, and were forme1·ly supposed to be bladders ; hence the specific name of vesieulosa. Stein observed that water-insects were sometimes. caught, and Prof. Cohn has recently found within the leaves of naturally growing plants many kinds. of crustaceans and larvre.t Plants which had been kept in filtered water were placed by him in a vessel con- * Since his original publication, Stein has found out that the irritability of the leaves was observed by De Sassus, as recorded in ' Bull. Bot. Soe. de F'mnc-e,' in 1861: Delpino states in a paper published m 1871 ("Nuovo <.:Hornale Bot. Ital.' vol. iii. p. 17 4) t~at "una quantita di chiocciohne e di altri animalcoli acquatici" are caught and suffocated by tho le::tvcs. I presume that r:hioccioUne are fresh-water molluscs. It would be interesting to know whether their shells are at all corroded by the acid of the digestive secretion. t I am greatly indebted to this distinguished naturalist for having sent me a copy of his memoir on Aldrovanda, before its publication in his 'Beitdi.ge zur Biologie der Pflanzen,' drittes Heft, 1875~ p. 71. y |
