131 

 THE CLIMATE OF EASTERN TASMANIA INDI- 

 CATED BY ITS LICHEN FLOEA. 



By Eev. F. R. M. Wilson, Kew, Victokia, Cor. Mem. 

 Roy. Soc, Tasmania. 



Durirg a visit of five weeks to Tasmania, in February and 

 March, 1891, while exploring for lichens in the 'neighbour- 

 hoods of Launceston, Mount Arthur, Ulverstone, Hobart, 

 Moant Wellington, the Huon River, and St. Mary's Pass, I 

 was struck with the general and unexpected poverty of the 

 lichen flora, and, on looking about for the cause of this, I 

 noted the evident frequency of bush fires, which are the most 

 destructive enemies of lichen growth. This, however, did 

 not wholly explain the matter, for, even where the plants 

 might be expected to recover from the action of the fire, their 

 vitality seemed to be checked by the drjness of the climate. 

 This was a discovery surprising to a Victorian, who had been 

 accustomed to consider the climate of Tasmania a humid one. 

 An examination of meteorological authorities, however, 

 showed that in the eastern portion of the island the rainfall 

 is rot only less than it is in the western, but less than it is in 

 Victoria. In the west and the highlands of Tasmania 75in. of 

 rain have been registered in one year, and the average of the 

 whole island is said to be 35in.; but the annual rainfall at 

 Hobart is only 21-52in. 



These adverse influences of fire and drought doubtless 

 react on one another, the fires thinning the forests and under- 

 growth, and thus lessening the rainfall, and the lack of rain 

 exposing the country to the ravages of fire. 



These influences, however, are considerably modified in the 

 eastern part of Tasmania by the altitude of the mountains 

 and by the ocean currents along the coast, both of which 

 have a great effect upon the geographical distribution of 

 lichens. 



When I visited Tasmania I was anxious to test a theory 

 which I entertained with regard to the distribution of lichens 

 in Australia. This theory was that the warm current from 

 the tropical Pacific Ocean, passing down the east coast of 

 Australia, carries southward the spores of tropical lichens 

 and the conditions favourable to their growth, until it is met 

 by the cold south-west seas and winds which greet the 

 traveller when doubling Wilson's Promontory from the east. 

 Nautical observations have determined the trend of this 

 coastal current, and traced it from the tropics southward 

 beyond Australia and along the eastern coast of Tasmania. 



K 



