BY A. A. HAMILTON. 491 



feet. On the dry salt plain, the Triglochin cannot maintain a 

 connected sward, breaking up into small mats or isolated tufts 

 which reach maturity and produce flowers and fruits when but 

 1—2 inches high (Plate xxviii., fig. 23) . 



On the opposite side of the river the scour sets in the direction 

 of the bank which is deeply eroded. A long strip of Thatch- 

 reed is here bisected by a band of Stir pus littoralis, each species 

 maintaining in a large measure the integrity of its formation, 

 an occasional rhizome of either species intruding its neighbour's 

 colony and signifying its presence by raising a solitary stem 

 (Plate xxv., fig. 17) . The struggle for supremacy between the 

 reed formations in this station is exceptionally severe, as their 

 root systems descend to an equal depth and compete for susten- 

 ance and space on the same plane. The Thatch-reed maintains 

 a large aerial growth, its tall culms carrying a quantity of 

 broad flag which places it at a disadvantage with its competitor, 

 whose narrow cylindrical leaves do not make a heavy demand 

 on the roots for support, but the compact rhizomatic system 

 of the Thatch-reed enables it to keep its more straggling op- 

 ponent at bay. In the deeper water the Thatch-reed is repro- 

 duced vegetatively, but the plants growing in the shallow marsh 

 mud frequently flower and fruit. 



Triglochin procera R.'Br., a flaccid-leaved, tuberous-rooted, 

 aquatic herb, endemic within the Commonwealth, occasionally 

 intrudes the open spaces of the formations of both Thatch-reed 

 and Scirpus, occupying in the deeper water a position similar to 

 that held by its smaller relative T. striata in the shallower 

 habitat on the marsh. T. procera is not as communal as its 

 congener and is one of the few perennial herbs frequenting the 

 estuary which has not connected its members either epigeally 

 or hypogeally by means of runners or rhizomes. The fruits of 

 T. procera have a brief flotation, the soft corky coat of the 

 carpels, though buoyant, is soon saturated, none floating longer 

 than 48 hours; the cylindrical seeds stripped of the coat sink 

 immediately . 



In a narrow tidal channel on the southern bank of Cook's 

 River which enters the marsh on the eastern side of Cook's 

 River Road, a ribbonlike formation of Azolla filiculoides Lam., 

 var. rubra Diels., was observed lining the muddy bank on either 

 side of the watercourse at high water mirk. When visited in 

 November (it is an aestival monocarp) the plants were resting 



