BY A. A. HAMILTON. 493 



Pine-forest. In a Casuarina forest at Bray's Bay on the Parra- 

 matta River, a carpet of branehlets was found several inches 

 thick, which had rendered the habitat almost untenable for 

 herbaceous vegetation. A sward of Salt-grass established on 

 the verge of the salt-plain had forced a passage some yards into 

 the forest by mechanical pressure, where the deposit was thin, 

 but its further progress was arrested by the accumulation of 

 dead branehlets. A few tufts of J uncus maritimus which had 

 entered the forest were able to develop in its precincts, their 

 strong, sharp-pointed leaves and stems pushing upwards through 

 the debris to secure the necessary illumination. The cylindrical 

 elongated branches of the Casvxirina, held vertically and regu- 

 larly-spaced, break the light in a manner suited to the require- 

 ments of the numerous epiphytes to which its protection is ex- 

 tended. On the banks of Tuggerah Lakes and the tidal channel 

 entering the Tom Thumb lagoon near Wollongong, the trunks 

 of the Casuarinas harbour dense masses of the Pencil Orchid, 

 Dendrobium teretifolium R. Br., in addition to the Lichens 

 which are invariably present. These trees are also exceptionally 

 subject to infestation by parasitic Loranths which frequently 

 reward their host by accomplishing its destruction. It is doubt - 

 less more than a coincidence that the leaves of the Pencil-Orchid, 

 and its associate Loranthus linophyllus Fenzl., (probably the 

 var. b. of Bentham* which has a coastal range from Brisbane 

 to the Illawarra), both of which have chosen ('. glauca as a host, 

 should simulate the cylindrical growth form of its branehlets. 



The seed-like nutlets of the Swamp-Oak are surmounted by a 

 membraneous wing and have a highly polished coat. The wing 

 is larger than the nut and would carry it a short distance from 

 the parent plant in a strong breeze, but is not adapted for a 

 lengthy flight. The nutlets of C. glauca floated for a week, the 

 varnished coat, though not ruptured, developing permeability at 

 an early stage of immersion. Nutlets of Casuarina distyla 

 Vent., which is not a halophytic species, sank within 48 hour* 

 The influence of the wing on buoyancy is inconsequential, fruits 

 from which the wings had been removed sinking in a like period 

 to those upon which it was retained, though it was noted that 

 the nutlets of ('. glauca floated wing upwards, and those of 

 ('. distyla with the wing downwards. 



* Flora Austr., iii., 394. 



