28 Armitagb, Plant Remains in OHvine-Basalt. [ ^'^june^'^' 



I procured all of the remaining portions of the specimen that 

 were available, but many pieces had been broken up along with 

 the surrounding basalt by the workmen and sent to the stone- 

 crushing machines. Logs of wood pyritized and partly carbonized 

 have not infrequently been uncovered from the ancient river 

 sands which underlie the basalt in this and other quarries about 

 Melbourne. In at least one case (ry) the genus and species of 

 the plant have been determined. A piece of basalt enclosed in 

 a gnarled stump was also obtained on this occasion. 



But the occurrence described in the present communication is, 

 as far as I have been able to ascertain, the only recorded 

 instance in Australia of plant remains being found actually in an 

 igneous rock. The pieces of which I am possessed were 

 necessarily broken in the operation of quarrying, but enough of 

 them remain to show that the charred wood is so closely clasped 

 in its stony covering that it looks as if the basalt had been 

 ingeniously grafted on to the wood. Not only is the contact 

 between the two remarkably close, but the basalt has, in fact, even 

 flowed into and filled up shrinkage cracks along the medullary 

 rays and around the annual rings of the wood, making it heavy, 

 and in parts quite solid. It is, as it were, filled with miniature 

 dykes and sills of basalt. The piece of wood when complete 

 must have measured at least three feet in length and seven to nine 

 inches in diameter. It has the appearance of a charred piece of 

 one of the Casuarinese, but further microscopic examination is 

 necessary before it can be definitely decided that it is so. 



Such examination of slices to be made later will doubtless 

 reveal other interesting features worthy of remark. As to the 

 method by which the wood became imprisoned in its stony 

 sheathing, it is not very difficult to realize that, as the lava, which 

 must necessarily have been extremely liquid, flowed and rolled 

 along the ancient Pliocene valley, it caught up and enveloped the 

 wood. The great heat drove off and caused the oxidation of the 

 hydrocarbons ; but before the carbon could become oxidized the 

 air supply was shut off by the molten lava surrounding, and 

 penetrating the shrinkage cracks of, the carbonized remains. 

 These were thus sealed up until revealed, having suffered no 

 further change than a slight pyritization. 



The age of these Yarra Valley basalts has been discussed by 

 Mr. A. E. Kitson (i8), who has come to the conclusion that 

 they are Newer Pliocene. The fossil wood described herein 

 would not come in the category marked (a) in the summary of 

 references on p. 26, which refer to occurrences of very recent 

 geological time, but would be placed with those marked (c) and 

 (d). At the last January meeting of the Club a piece of the wood 

 enclosed in the basalt was shown (19), and at the March meeting 

 a microscopic rock slice, showing the junction of the wood and 

 basalt, was exhibited (20). 



