Europe, open under a sufficiently high temperature, and, when touched,
suddenly close.* They re-expand in from 24 to 36 hours, but only, as it
appears, when inorganic objects are enclosed. The leaves sometimes
contain bubbles of air, and were formerly supposed to be bladders;
hence the specific name of vesiculosa. 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 larv .** 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. Soc. de France, in 1861. Delpino states in a paper
published in 1871 ( Nuovo Giornale Bot. Ital. vol. iii. p. 174) that
una quantit di chioccioline e di altri animalcoli acquatici are
caught and suffocated by the leaves. I presume that chioccioline are
fresh-water molluscs. It would be interesting to know whether their
shells are at all corroded by the acid of the digestive secretion.
** I am greatly indebted to this distinguished naturalist for having
sent me a copy of his memoir on Aldrovanda, before its publication in
his Beitrage zur Biologie der Pflanzen, drittes Heft, 1875, page 71.
[page 322]
taining numerous crustaceans of the genus Cypris, and next morning many
were found imprisoned and alive, still swimming about within the closed
leaves, but doomed to certain death.
Directly after reading Prof. Cohn s memoir, I received through the
kindness of Dr. Hooker living plants from Germany. As I can add nothing
to Prof. Cohn s excellent description, I will give only two
illustrations, one of a whorl of leaves copied from his work, and the
other of a leaf pressed flat open, drawn by my son Francis. I will,
however, append a few remarks on the differences between this plant and
Dionaea.
Aldrovanda is destitute of roots and floats freely in the water. The
leaves are arranged in whorls round the stem. Their broad petioles
280