154 PHYSIOGNOMY OF PLANTS. 



of which 165 belong to the northern and 51 to the 

 southern hemisphere. Since my researches these pro- 

 portionate numbers must be modified, as, including the 

 species of Pinus, Cupressus, Ephedra, and Podocarpus, 

 found by Bonpland and myself in the tropical parts of Peru, 

 Quito, New Granada, and Mexico, the number of species 

 between the tropics rises to 42. The most recent and ex- 

 cellent work of Endlicher, Synopsis Coniferarum, 1847, 

 contains 312 species now living, and 178 fossil species found 

 in the coal measures, the bunter-sandstone, the keuper, and 

 the Jurassic formations. The vegetation of the ancient world 

 offers to us more particularly forms which, by their simul- 

 taneous affinity with several different families of the present 

 vegetable world, remind us that many intermediate links 

 have perished. Coniferse abounded in the ancient world : 

 their remains, belonging to an early epoch, are found espe- 

 cially in association with Palms and Cycadese ; but in the 

 latest beds of lignite we also find pines and firs associated 

 as now with Cupuliferse, maples, and poplars. (Kosmos, 

 Bd. i. S. 295-298, and 468-470 ; Engl. edit. p. 271-274, 

 and Ixxxix.) 



If the earth's surface did not rise to considerable eleva- 

 tions within the tropics, the highly characteristic form of 

 needle-leaved trees would be almost unknown to the inha- 

 bitants of the equatorial zone. In common with Bonpland 

 I have laboured much in the determination of the exact 

 lower and upper limits of the region of Coniferse and of 

 oaks in the Mexican highlands. The heights at which both 

 begin to grow (los Pinales y Encinales, Pineta et Querceta) 



