Sept., 1908.] THE VICTORIAN NATURALIST. 81 



Various adaptations for surviving periods of drought are shown, 

 such as the formation of reduced evaporating surfaces and fleshy 

 leaves like those of the salt-bushes, by the transformation of 

 branches which would bear leaves into thorns and prickles, such 

 as Acacia armata, &c. 



In addition, many herbaceous perennials in dry seasons or situa- 

 tions develop as annuals, surviving the dry period in the form of 

 seed. The seeds of many Leguminosse (Acacias^ Jachsonias, 

 Viminaria denudata, &c.) have impermeable cuticularized seed- 

 coats when fully ripened, so that they may remain dormant in the 

 soil for long periods of years, germinating when brought to the 

 surface and the coats softened by heat, by the alkaline ash of bush 

 lires, or by mechanical abrasion. 



A few introduced trees, such as the More ton Bay Fig, Maple, 

 and Plane, shed a portion of their leaves in drought so that the 

 remainder may have a chance of surviving, and the same may be 

 shown to a limited extent by some of the native trees, although 

 the latter are nearly all evergreen, the leaves being shed irregularly 

 all the year round without ever leaving the tree entirely bare. The 

 erect, branchless, lower stems and thick fibrous bark of so many 

 of our Eucalypti are probably protective adaptations against bush 

 fires, and this peculiarity often causes them to be unaftected 

 by a fire which would completely consume a European pine 

 forest under similar conditions. The frequently delayed de- 

 hiscence of Callistemon, Hakea, Banksia, &c., especially under 

 moist conditions, is probably also an adaptation to drought 

 conditions or to recurrent bush-fires, for both causes clear the 

 land of existent vegetation to a greater or less extent, and, at 

 the same time, excite the escape by dehiscence of the seeds which 

 are to replace it, and the germination of those dormant seeds 

 whose coats have been softened by the heat and ashes. 



The coast scrub of Tea-tree (Leptospermum and Melaleuca) pro- 

 tects itself against wind and sand-drift by growing close together, 

 the leaves, which demand a fair exposure to light, being found 

 at the upper surfaces and edges of the scrub only, and giving its 

 interior a peculiarly gloomy character. Where the scrub is dense, 

 no plants grow beneath ; but where it is less dense a few mosses, 

 grasses, and such orchids as Caladenia, Pterostijlis, &c., may be 

 found, and an introduced Polygala, P. myrtifolia, L., is some- 

 times abundant. The Mallee scrub of the north-west (shrubby 

 Eucalypti) affords an instance of similar adaptation, but in this 

 case to inland conditions. 



In spite of its close connection with the rest of Australia, the 

 barriers to migration in the past have sufficed to enable Victoria 

 to retain a fairly large number of endemic species, at least 46, 

 although possibly some of the latest-described plants may prove 

 to be merely varieties or hybrids of species with a wider range. 



