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outside Tasmania, and it extends only to Victoria and New 

 South Wales. Tasmania is exceptionally rich in species of 

 plants that are confined to its area. 



We have noticed that in Wattles and Myrtles the foliage 

 is greatly reduced and otherwise modified to suit a climate 

 of excessive sunlight. In the interior of Australia it may 

 be an adaptation to dry soil conditions, but there is no 

 reason to assume that dryness has been the main factor 

 with us. A clear dry atmosphere with considerable tem- 

 perature is injurious to broad delicate leaves; but in our 

 Saxifrages, though the leaves are not very delicate, they 

 do not show any great effort to reduce exposed surface 

 and evaporation. This mixture of broad-leaved forms 

 suited to mean climatic conditions with others modified to 

 withstand excess is found also through all coastal districts 

 of temperate Australia. We find in these districts that 

 broad-leaved European plants do well; they are not much 

 affected even in a hot, dry summer, provided root moisture 

 does not sink too low. In other words, Tasmania and the 

 coast of Australia have now a climate suited to broad- 

 leaved plants. Why have we then a preponderance of 

 reduced, thick-leaved types? Are they the survival of a 

 former condition, or are they migrants whose hardy nature 

 has enabled them to oust more efficient but less vigorous 

 species ? The migration of plants is a most interesting 

 study, but conclusions should not be formed hastily. 



A plant, other than one only suited to live in water, 

 is proivded with a skin which is somewhat analogous to 

 the skin of an animal. Its two principal functions are to 

 protect the soft parts from injury, and to reduce indis- 

 criminate evaporation. Except in some lowly plants, as 

 Mosses, death will ensue if dried by excessive evaporation. 

 The skin effectively prevents this, but as a thick skin 

 brings special disadvantages with it, we generally find 

 species of plants whose natural habitat is a moist, shaded 

 place, or a country with a persistently cloudy sky, have 

 thin skins. Even the same plant will often respond to 

 these conditions, developing a thinner skin if grown in 

 shade than when freely exposed. Though the skin is never 

 absolutely impervious, it is nearly so. In a plant well 

 suited to its surroundings practically no evaporation takes 

 place from the surface ; but a plant, in order to live, must 

 draw in through its roots a great quantity of water with 

 dissolved material. And it must get rid of this water by 

 evaporation from its green surface, or the absorption will 

 soon come to a standstill. This evaporation is carried out 



