150 Mr. E. J. QuEKETT on some Fossil Woods. 



a palm, I discovered a portion which, instead of being compact like the gene- 

 ral mass, broke down on the slightest pressure into minute fragments: on 

 submitting these to the microscope, it was found that they were composed of 

 cylinders more or less elongated and minute rounded granules. On the cy- 

 linders there could readily be observed a perfect screw, the helix being either 

 single or compound, and undoubtedly fashioned from the interior of the 

 recent spiral vessels, which fact gives the most satisfactory proof that the 

 fibre is in the interior of the cylinder, as these siliceous casts could not have 

 been so moulded if the spiral fibre had been external. The intervals between 

 the helix show the shape of the fibre, and also show that it was of a solid 

 nature. 



The other point that has occasionally been the subject of controversy, is 



the nature of the discoid bodies on the woody tissue of coniferous plants. 



These have been supposed by some persons to be glands ; by others to be 



thicker, and by others again to be thinner places in the membrane forming 



the walls of the woody fibres. Others have asserted that there is a pore in 



the centre of each disc, which allows of a communication between adjoining 



fibres. Later observers however have shown that none of the above theories 



is altogether correct, as the discs are not proper to one woody fibre, but are 



formed between two contiguous fibres, each contributing to the formation of 



the disc by having a minute depression, shaped like a saucer, on its exterior, 



which corresponds exactly to a similar depression on the contiguous fibre, 



whereby a small cavity is left between them. These markings or cavities 



very rarely exist on the sides of the fibres opposed to the pith or bark, but 



are very numerous on the sides parallel to the medullary rays. Wherever the 



markings occur, the saucer-shaped depression is thick at the circumference 



and for some distance towards the centre ; but in the centre itself there is a 



spot so extremely thin and minute, that the light, which has to pass through 



it, becomes decomposed, and the spot looks either green or red, according to 



the adjustment of the focus. 



Having received from Professor Bailey a specimen of fossil wood which 

 was found at Fredericsberg in Virginia, I perceived, on submitting it to the 

 microscope, that it would easily break into minute fragments in the direction 

 of the woody fibres, which, when carefully viewed, presented a most beautiful 



