330 VIEWS, &C. PHYSIOGNOMY OF PLANTS. 



the vital heat of the Aruin cordifolium rises in the Isle of 

 France to 110 or 120, whilst the temperature of the sur- 

 rounding air is only 66. 2 Fahr. Even in Europe, Becquerel 

 and Breschet found a difference of 39. 4. Dutrochet observed 

 a paroxysm, a rhythmical decrease and increase of vital 

 heat, which appeared by day to attain a double maximum. 

 Theodore de Saussure remarked analogous augmentations of 

 heat, although only of l.l and 1.8 Fahr., in other families 

 of plants ; as, for instance, in Bignonia radicans and Cucurbita 

 pepo. In the latter, the male plant exhibited a greater in- 

 crease of temperature than the female, when measured by a 

 very sensitive thermoscopic apparatus. Dutrochet whose 

 early death is greatly to be regretted, on account of the import- 

 ant services he rendered to physics and vegetable physiology 

 likewise observed,** by means of thermo-magnetic multipli- 

 cators, a vital heat of 0.25 to 0.67 Fahr. in many young plants 

 (Euphorbia lathyris, Lilium candidum, Papaver somniferum), 

 and even among funguses, in many species of Agaricus and 

 Lycoperdon. This vital heat disappeared at night, but not 

 by day, even when the plants were placed in the dark. 



The contrast presented by the physiognomy of the Casua- 

 rineas, acicular-leaved trees, and the almost leafless Peruvian 

 Colletias and Pothos plants (Aroideas), is still more striking 

 when we compare these types of extreme contraction in the 

 leaf form with Nympha3acea3 and Nelumbonese. Here we 

 again meet, as in the Aroidese, with leaves in which the 

 cellular tissue is excessively expanded upon long, fleshy, suc- 

 culent petioles, as Nymphaea alba, N. lutea, N. thermalis 

 (formerly called N. lotus, from the hot spring of Pecze, near 

 Groswardein in Hungary), the species of Nelumbo, Euryale 

 amazonica (Poppig), and Victoria Regina, allied to the prickly 

 Euryale, although of a very different genus, according to 

 Lindley, and discovered in 1837 by Sir Robert Schomburgk 

 in the river Berbice, in British Guiana. The round leaves of 

 this splendid aquatic plant are from 5 to 6 feet in diameter, and 

 surrounded by upright margins from 3 to 5 inches in height, 

 which are light green on the inner side, but of a bright 

 crimson on the outside. These agreeably perfumed flowers^ 

 of which 20 or 30 may be seen together in a small space, are 

 about 15 inches in diameter, of a white or rose colour, and 



* Comptes rendus de I'lnstitut, t. yiii. 1839, p. 454, t. ix. pp. 614 

 781. 



