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 officinalis, belonging to the botanical order of the Verbenacee, 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 Rhizophoree, which, in this instance, includes several 
other genera, ¢.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, 
