ANNOTATIONS AND ADDITIONS. 333 



as Joseph Hooker has shown (Flora Antarctica, p. 229), the strik- 

 ing example of the uninterrupted extension of the same species of 

 tree from the most southern part of Tierra del Fuego and Hermit 

 Island, where it was discovered by Drake's Expedition in 1577, to 

 the northern highlands of Mexico; or through a range of 86 degrees 

 of latitude, or 5160 geographical miles. Where it is not birches 

 (as in the far North), but needle-trees (as in the Swiss Alps and the 

 Pyrenees), which form the limit of arborescent vegetation on the 

 highest mountains, we find above them, still nearer to the snowy 

 summits which they gracefully enwreath with their bright garlands, 

 in Europe and Western Asia, the Alp roses, the Rhododendra, 

 which are replaced on the Silla de Caracas and in the Peruvian 

 Paramo de Saraguru by the purple flowers of another genus of Eri- 

 caceae, the beautiful race of Befarias. In Lapland, the needle-trees 

 are immediately followed by Rhododendron laponicum; in the Swiss 

 Alps by Rhododendron ferrugineum and R. hirsutum; in the Pyre- 

 nees by the R. ferrugineum only; and in the Caucasus by R. cau- 

 casicum. Decandolle found the Rhododendron ferrugineum growing 

 singly in the Jura (in the Creux de Vent), at the moderate altitude 

 of 3100 to 3500 (3304 to 3730 E.) feet, 5600 (5968 E.) feet lower 

 down than its proper elevation. If we desire to trace the last zone 

 of vegetation nearest to the snow line in the tropics, we must name, 

 from our own observations, in the Mexican part of the tropical zone, 

 Cnicus nivalis and Chelone gentianoides ; in the cold mountain 

 regions of New Granada, the woolly Espeletia grandiflora, E. corym- 

 bosa and E. argentea; and in the Andes of Quito, Culcitium rufes- 

 cens, C. ledifolium, and C. nivale, yellow flowering Composite, 

 which replace in the last-named mountains the somewhat more 

 northerly Espeletias of New Granada, to which they bear a strong 

 physiognomic resemblance. This replacement, the repetition of re- 

 sembling or almost similar forms, in countries separated either by 

 seas or by extensive tracts of land, is a wonderful law of nature 

 which appears to prevail even in regard to some of the rarest forms 

 of vegetation. In Robert Brown's family of .the Rafflesiese, sepa- 

 rated from the Cytinese, the two Hydnoras described by Thunberg 

 and Drege in South Africa (H. africana and H. triceps) have their 

 counterpart in South America in Hydnora americana (Hooker)." : "->- 



