64 PHYSIOGNOMY OF PLANTS. 



parts of which the whole consists forming a number of 

 organically distinct individuals. In the group of Phyto- 

 corals these individuals cannot detach themselves at pleasure, 

 but remain united with each other by thin plates of carbonate 

 of lime. It is not, therefore, by any means the case that 

 each trunk of coral has a central point of common vitality or 

 life. (See Ehrenberg's Memoir above referred to, S. 419.) 

 The propagation of coral-animals takes, place, in the one 

 order, by eggs or by spontaneous division ; and in the other 

 order, by the formation of buds. It is the latter mode of 

 propagation which, in the development of individuals, is the 

 most rich in variety of form. 



Coral-reefs, (according to the definition of Dioscorides, 

 sea-plants, a forest of stone-trees, Lithodendra), are of three 

 kinds ; coast reefs, called by the English " shore or fring- 

 ing reefs," which are immediately connected with the coasts 

 of continents or islands, as almost all the coral banks of 

 the Red Sea seen during an eighteen months' examination 

 by Ehrenberg and Hemprich; "barrier-reefs," "encir- 

 cling-reefs," as the great Australian barrier-reef on the 

 north-east coast of New Holland, extending from Sandy Cape 

 to the dreaded Torres Strait; and as the encircling-reefs 

 surrounding the islands of Vanikoro (between the Santa 

 Cruz group and the New Hebrides) and Poupynete (one 

 of the Carolinas; and lastly, coral banks enclosing 

 lagoons, forming " Atolls" or " Lagoon-islands." This 

 highly natural division and nomenclature have been in- 

 troduced by Charles Darwin, and are intimately con- 

 nected with the explanation which that ingenious and 



