170 



Mr. Hinds on Climate in connexion 



ing. James, in the expedition to the Rocky Mountains, re- 

 lates seeing Conferva and "other vegetables" growing in the 

 numerous thermal springs at the base of the Ozark mountains, 

 with the temperature from 92° to 140°. The last two in- 

 stances are not, however, very remarkable, when we call to 

 mind the heat to which vegetation is exposed in low latitudes 

 from the direct power of solar radiation. Sir \V. J. Hooker 

 has supplied us with some very interesting facts respecting 

 the vegetation near hot springs in Iceland, and especially the 

 Geysers, the temperature of which is equal to boiling water. 

 On a heated bank where they were exposed to the steam, 

 Conferva vaginata, Gymnostomum fasciculare, Fissidens hy- 

 pnoides, and Jungermannia angulosa, flourished in the greatest 

 perfection. At the Geysers, "close to the edge of many of 

 the hot springs, and within a few inches of the boiling water, 

 in places which are consequently always exposed to a consi- 

 derable degree of heat, arising both from the water and the 

 steam, I found Conferva limosa" In a similar situation, an 

 Oscillatoria, and Jungermannia angulosa. Again, in water of 

 a " very great degree of heat," Conferva flavescens ; and an- 

 other species, Riccia glauca, was also found on a surface con- 

 siderably heated. All these plants, excepting the doubtful 

 expression of James, belong to families of the simplest struc- 

 ture, and whose members have the widest geographic limits ; 

 among plants they appear those least affected by extremes of 

 temperature. 



Plants of more complex organization have likewise been 

 found in similar situations, but not with the habitual frequency 

 of the agamic families. The thermal springs of Trinchera, 

 near Valencia, have a temperature as high as 1 94° ; vegetation 

 of surpassing luxuriance surrounds them, and the roots of spe- 

 cies of Mimosa, Clusia, and Ficus are bathed by their w aters. 



Under opposite circumstances vegetation hardly thrives so 

 well, still it is capable of enduring great depressions of tem- 

 perature*. Thermometers placed in the trunks of trees have 

 stood below the freezing point. In the arctic regions flowers 

 struggle through the melting snows, and one plant has its 

 existence even in the snow itself, where it vegetates, repro- 

 duces its species, and decays. Proiococcus nivalis has been 

 found in the snows of the arctic regions, among the Alps and 

 Pyrenees, and in other situations in Europe ; of late years it 

 has also been observed among the islands to the south of 

 Cape Horn. In low latitudes plants are often subject to an 

 unexpected depression; I have already mentioned casually 



* This subject lias lately been treated of by M. Morren. See ' Observa- 

 tions Anatomiques sur la congelation des Organes des Vegetaux.' — Bul- 

 letins de l'Acad. de Bruxellcs, t. v. p. 64. — Ed. 



