54 REVIEWS. 



hundreds of square miles, from the western districts to Port Natal. The 

 same may be said of many of the Proteacese, both of the Cape and of 

 Australia. Every district, of no great extent, supplies its own peculiar 

 6pecies. Even some genera, such as Franklandia and Bettendena, 

 are confined to very small areas. Clianthus puniceus, so well known in 

 our gardens, is much more likely to be preserved in cultivation than in 

 New Zealand, its native country, where its range is very limited. 



The causes operating on the natural extension of species are summed up 

 under three heads, namely : — transportation, more or less easy, or more or 

 less frequent, of seeds in a germinating state, such transportation being 

 effected either by currents, or incidentally through the agency of animals 

 or man ; connection or separation more or less real of countries having 

 more or less analogous climates ; and lastly (and, as we believe, chiefly'), 

 the physiological peculiarities of each individual species. Besides these 

 actually existing causes, others may have formerly operated ; for example, 

 there may have been different means of transport at another geological 

 epoch ; islands now widely separated from continents may have formerly 

 been connected ; some species, very widely dispersed, may have an earlier 

 date in creation than others ; or the original number of individuals of 

 different species may have been different ; for we need not necessarily 

 suppose, in the vegetable kingdom at least, that every species spring 

 from one or two individuals. 



The changes which take place in the habitats of species form the sub- 

 ject of the eighth chapter. The question of naturalization* is largely dis- 

 cussed, and copious lists are given of species naturalized at short or at long 

 distances from their native localities. Some of these species, now widely 

 dispersed, are of recent introduction. Mimulus luteus, introduced from 

 North America to our gardens so lately as 1812, has been found "appa- 

 rently wild" in many parts of the Highlands of Scotland. We have also 

 seen it in the Wicklow mountains ; and M. de Candolle states that it has 

 spread along the streams in many valleys of the Vosges. Its American 

 habitat is extensive, reaching from Unalaschka, on the north, to Chili. 

 (Enothera biennis (the " evening primrose"), a native of North America, 

 introduced 1619, has become so disseminated over the greater part of 



* At p. 714. the author makes a strange blunder in confounding Stratiotes aloi- 

 des, Z., with Pistia stratiotes, L. Which of these plants is naturalized in the tanks 

 at Marly, we cannot say; but it is Pistia stratiotes — not "Stratiotes aloides," 

 as stated — which is a native of the Molluccas, Java, Malabar, and other intra- 

 tropical countries. Stratiotes aloides, we need hardly say, is a well-known European 

 plant, and a native of England. 



