28 HENRY G. SMITH. 



the three stages of the bark of one individual tree of E. 

 oreades rather discounts this supposition, and suggests the 

 idea that under ordinary conditions the Eucalypts use up 

 the calcium oxalate first formed. Certainly it does not 

 appear to be shed with the bark, and in this respect differs 

 from trees which throw off with their leaves the calcium 

 oxalate formed. 



The following results show this clearly : — 



(a) Fresh living bark 2 cm. thick; calcium oxalate = 1*37°/° 



(b) Thin ribbon bark 1 mm. thick; „ =0'025°/» 



(c) Thicker dead bark at base of 



trunk which was quite brown 



and 3 to 6 mm. thick ; ,, nil 



A smooth -bark tree was chosen because most of the 

 Mallees have a smooth bark, or at most a little persistent 

 bark at the base of the tree, or resemble the Boxes, and 

 all have the general characteristics belonging to the larger 

 trees of these classes. The Stringybarks do not appear to 

 take on the Mallee form of growth, and some of the largest 

 trees in Australia are species approaching this class. 



That the solution from which the crystallised calcium 

 oxalate was formed must have contained oxalic acid in 

 excess, and thus be more or less poisonous, is indicated by 

 the symmetrically formed crystals, and these crystals, too, 

 belong to a form and have a constitution different from the 

 calcium oxalate usually found in plants. The form peculiar 

 to Eucalyptus barks contains one molecule of water, and 

 has the composition and crystalline form of the mineral 

 Whewellite, with which substance it is perhaps identical. 



In the banana and other plants calcium oxalate occurs 

 in needle-like crystals or raphides. In the root of the 

 Turkey rhubarb, as well as in other plants, it occurs in 

 crystals having a conglomerate form, and these are also 

 found in some members of the cactus tribe, in Phytolacca 



