CENSUS OF EXISTING SPECIES. 101 



specific rank of two is doubtful. In Xortli America, north of the 

 39th parallel, a similar paucity of species exists-, the whole number 

 probably not exceeding a dozen. Whilst the coniferous vegetation of 

 the northern portions of the two continents was thus affected by the Glacial 

 period, the floras of the contiguous regions, as the Mediterranean Basin, 

 China and Japan, Xortli America west of the Rocky Mountains and 

 south of the 39th parallel on the east side were, as they still are, 

 exceptionally rich in coniferous genera and spesies. Much less is known 

 of the geological changes that have taken place in the south Temperate 

 /one, but whatever may have been their nature, their influence on the 

 vegetation, on account of the restricted land area, would he comparatively 

 small to what lias taken place in the north. As regards the existing 

 Conifer* of southern lands, none of the species cover large areas, and 

 the genera and species are much more varied than in the north. In 

 Tasmania the species are so local and present so few individuals, that 

 the island may be crossed from north to south without a single species 

 of the Order being met with.* In Xew Zealand, on the Contrary, the 

 < 'onifersB attain their maximum of numbers in the southern hemisphere, 

 snid, till recently, the fifteen or sixteen species which inhabit the islands 

 .covered nearly two-thirds of their area. In southern Chile a considerable 

 part of the slopes of the Andes is covered with a coniferous vegetation 

 represented by nine species distributed among six genera. In the 

 tropical regions of both hemispheres, coniferous trees form but a minute 

 fraction of the entire arborescent vegetation ; the few that occur are 

 chiefly Podocarps which nowhere form a continuous forest. Pinus is 

 represented by about half-a-dozen outlying species in the Indo-Malayan 

 region and in Central America; Agathis by nine and the African genus 

 Widdringtonia by five. Some of the Australian Araucarias and 

 Callitrids also occur within the Tropics. 



The number of existing genera and species has been variously 

 estimated. The genera admitted in this Manual are Taxacete eleven 

 and Conifeme twenty-five which with three exceptions in the Conifers 

 coincide with those admitted by Dr. Maxwell T. Masters in his recent 

 revision of the two Orders: These exceptions are the Glyptostrobus 

 of Endliclier which, following Bentham, is included in Taxoclium, and the 

 Pseudotsuga and Keteleeria of Carriers which are provisionally joined 

 into one genus Abietia. The monotypic Taxacl, Pherosphaira and the 

 coniferous genera Tetraclinis, Callitris, Actinostrobus and Widdringtonia 

 as well as all tropical and many sub-tropical species included in other 

 genera are omitted in the body of the work on account of their being 

 unsuited for cultivation in Great Britain. The following enumeration 

 of the species may be accepted as approximately correct so far as our 

 present knowledge extends and subject to such modification as the 

 views of different botanists respecting the limitation of species are 

 accepted. The regions are, to some extent, artificially defined, but the 

 limits assigned to them are such that, with the exception of one or 



* Sir J. I). Hooker. Flora of Tasmania, ]>. 349. 



