VEGETABLE VAGARIES. 275 



Towards the vagaries of the vegetable world the somewhat heterogeneous group 

 of the Mangroves contributes a conspicuous instalment. Although by no means 

 restricted to Australia, being abundant in innumerable varieties throughout all tropical 

 coasts and estuaries, the northern sea-board of this Island-Continent is especially 

 fertile in both specific types and individual developments. Mangroves, as a concrete 

 group, do not pertain to any special family, or even order, of the vegetable kingdom. 

 They have been correlated under a common title with reference only to the circumstance 

 that their habitats and environments have induced their collective assumption of 

 corresponding or closely parallel structural adaptations. All Mangroves, in the 

 popularly accepted sense of the term, agree with one another in being inhabitants of 

 the foreshores of coast-lines and river estuaries under such conditions that they are 

 subject to being, alternately, partially submerged and completely exposed to atmos- 

 pheric influences with the rise and fall of the tide. Two of the most abundantly 

 distributed representatives of the mangrove tribe are represented in the lower figure 

 of Plate XLIX. 



The lighter-barked tree in the centre is the so-called White Mangrove, 

 Avicennia, offlcinalis, belonging to the botanical order of the Verbenaceae, a group that 

 includes the handsome cultivated Lantanas. Flanking each side of this tree are 

 characteristic growths of the Red or Orange Mangrove, Rhizophora mucronata, 

 belonging to the order of the Rhizophorese, which, in this instance, includes several 

 other genera, e.g., Ceriops and Bruguiera, that participate in corresponding Mangrove 

 habits. The essential features in each of the two species figured is the peculiar 

 modification of their root elements. In Avicennia, the central form, the radiating 

 course of the horizontal slightly submerged roots from the central trunk is distinctly 

 traceable to a considerable distance by the outgrowth therefrom of vertical, thickly 

 crowded, shoot-like developments, popularly known as " Cobbler's pegs," which, 

 penetrating the superincumbent soil, attain to the height of from about one foot to 

 eighteen inches above it. To the uninitiated, it would scarcely occur that this mass 

 of vertical twigs was other than a luxuriant development of the suckers or root shoots 

 by which so many plants ordinarily propagate and extend their borders. 



The interpretation of the true function of these vertical growths would appear to 

 have been first arrived at by the late Dr. James Bancroft, of Brisbane, Queensland, 

 who contributed the account of some interesting investigations he made to the 1888 

 Meeting of the Australian Association for the Advancement of Science. One day, 

 when examining the shore in the vicinity of Avicennia growths at half tide, 



