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Analyses of Books. [July 



sider separately under taxonomy, the elementary organs, viz. the 

 cells, vessels, the organs of vegetation or the roots, trunks and 

 -leaves, and the organs of re-production, or flowers, fruit, and seeds, 

 and to deduce the natural method in accordance with these three 

 classes of organs. He explains then witl^ great precision all that 

 concerns the subordinary parts of the organs of nutrition and re-pro- 

 duction ; he points out among vegetables the degrees of resemblance 

 or association, and among the natural groups, the affinities existing 

 among themselves and with other groups, and he finishes by com- 

 paring the systems of classification. 



But the most curious and novel part of the work is that which 

 relates to botanical geography. The general laws of this distribu- 

 tion are, that vegetables increase in number and dimensions, in pro- 

 portion as we advance from the poles to the equator ; that the annual 

 species are more extended in the temperate zones and the woody 

 plants in the tropics ; that certain localities are affected exclusively 

 by certain families or tribes, or even by certain genera of these 

 families or tribes ; that in dividing the surface of the globe into forty- 

 five regions, bounded by mountains, seas, or deserts, we find each 

 region almost characterized by distinct families ; the dicotyledonous 

 plants being more numerous when the country is hotter, and the 

 monocotyledonous when the district is colder ; that islands have a 

 vegetation increasing in peculiarity as they are more isolated 

 and removed from continents. That consequently we may regard 

 these regions as so many centres from which have proceeded so 

 many vegetable creations of families, tribes, and peculiar genera.^ 



These families, tribes, genera, and species, are diff*erently mixed 

 by the effect of winds, rivers, and currents, and especially by birds 

 which have transported here and there, and particularly in the 

 neighbouring regions, seeds which at first belonged to one country 

 alone. Sometimes, however, these creations generally so distinct, 

 co-exist in distant localities, a fact, which cannot be explained by any 

 of these agencies. Thus the Primula farinosa and Poa alpina, 

 are found in the neighbourhood of the two poles at the Malouine 

 islands (Melvin,) and on mountains in Europe, and are not met 

 with in the intermediate countries. 



Genera are rich in species in proportion to the heat of the country, 

 and these species are often divided into sections possessing peculiar 

 climates. Thus the Saxifraga, Anemones, and Rhododendrum, 

 * &c. of Europe, are diflTerent from those of the Himalaya mountains, 

 and our oaks are distinct from the species of North America. Some- 

 times also the same genus has species dispersed in different regions. 

 Thus the three species of Trollius inhabit respectively, Europe, 

 Asia, and America. The species have a distribution more or less 

 extensive, and this distribution possesses a centre or a point in which 

 they abound in greatest quantity, and from which they become 

 rarer and gradually disappear. An exception must of course be 

 made in favour of those cultivated by man, and those naturalized 

 around human habitations as Urtica urens, Chenopodia, &c. 



The Amphigamous order, in the class Cri/ptogamia, which have 

 very obscure sexual organs, are not limited by botanical regions. 



