INTRODUCTORY ESSAY. 187 



sun-power, to which the open nature of many of the valleys 

 contributes in no small degree. 



The principal plants of the tropical zone of Nipal belong to 

 a less humid type than those of Sikkim, and are abundant all 

 over the subtropical mountains of India, where a dry and wet 

 season alternate. The commonest trees are Moringa, Putran- 

 jiva, Bombax, Vatica robusta, Buchanania, Spondias, Butea 

 frondosa and parviflora, Erythrina, Acacia Lebbek and stipu- 

 laris, Bauhinia purpurea and Vahlii, Ventilago, Conocarpus, 

 Terminalia, Nauclea cordifolia, and Ulmus integrifolia. 



In the plain of Kathmandu, which is elevated 4000 feet, 

 the ground is in a great measure under cultivation, and the 

 hills are bare of trees. The vegetation and climate are there- 

 fore subtropical, and from the position of the Kathmandu 

 plain, close to the ridge of the spur which separates the ba- 

 sins of the Gandak and Kosi, its mean level is probably 

 greater than that of many of the valleys of both rivers, and 

 of the ridges which separate their tributaries. 



In the temperate flora of central Nipal, for the same rea- 

 son, the Japanese and Malayan types are much fewer ; En- 

 kianthus, Stachyurus, Vaccinia, Aucuba, Helwingia, several 

 Rubi, and Rhododendron JDalhousiee and Edgeworthii being aU 

 absent, while European and west Himalayan forms which are 

 wanting in Sikkim make their appearance. In the extreme 

 east of Nipal, in the valley of the Tambar river, Ehododen- 

 drons are scarcely less abundant than in Sikkim; but those 

 of the temperate zone are certainly entirely wanting in that 

 part of central Nipal from which Dr. Wallich obtained his 

 collections, with the exception of R. arboreum, which is found 

 throughout the whole Himalaya, R. barbatum, which extends 

 to Kumaon, and R. campanulatum, which is a subalpine spe- 

 cies. The more alpine species cannot be so positively affirmed 

 to be absent, but it is highly probable that the number of 

 species is not great, none having been obtained by Dr. Wal- 

 licFs collectors, but such as are universally distributed 

 throughout the Himalaya. The pines are the same as those 



