THE AUSTRALIAN GREY MANGROVE. 263 



were inclined at an angle (more or less acute) with the 

 foreshore. It was at first thought to be due to prevailing 

 winds, but this, however, was found not to be the cause. 

 Next, it was observed that the leaves of all the trees were 

 disposed towards the north, — a case of heliotropism appar- 

 ently, and the question naturally arose, why ? The answer 

 came in the observation, that by such an orientation, the 

 pneumatophores were in shade, and so it worked out that 

 the directing influence was to shade these breathing organs, 

 and in order to get this protection, the stem, but more 

 often the branches, grew in whatever direction this shade 

 was obtainable. It was also noted that wherever the 

 breathing roots became exposed for a length of time to 

 the sun's rays, they perished, and then the branches on 

 that side of the tree died and fell off, — a truly botanical 

 sympathy. Judging from the structure, the storage of a 

 large amount of water is also an important function of 

 these leaves. 



The knowledge of this necessity for the natural shading 

 of the pneumatophores can now be turned to some economic 

 purpose. These breathing roots are of great value to 

 the oyster cultivator, as the crop of oysters to be obtained 

 from them is greater than from any material used, such as 

 slates, stone, etc., and consequently great efforts are made 

 to cultivate this mangrove, but it has always been found 

 difficult to start a plantation on a treeless shore, the youug 

 plants soon dying or putting on such slow growth as to 

 be almost useless. Since discovering that shade is requisite 

 for the growth of these organs, action is about to be com- 

 menced to introduce artificial shade until trees attain some 

 size, or at least sufficient foliage to make its own shade 

 protection, and these efforts will be watched with much 

 interest by the commercial people concerned in oyster 

 culture. 



(c) Economics. — Cattle eat the leaves with great relish. 



