94 
and geometry of the propeller blade will, ere long, give an 
answer sufficiently accurate for all practical purposes. The 
Council of the Society of Naval Architects have promised a 
Gold Medal to the best solution during the year 1879. 
Dr. R. Angus Smith, F.RS., exhibited a section of a 
large Eucalyptus globulus, and drew attention to the pecu- 
liar arrangement of the fibres in the different rings of the 
wood. 
Professor W. C. Williamson, F.RS., pointed out that the 
peculiarities in the section of the Eucalyptus exhibited by 
Dr. Smith arose from differences between the inner and 
outer portions of each annual ring of the wood. In most 
plants the fibro -vascular structures of the inner portion 
and the sclerencliymatous wood-cells of the outer one had 
their axes parallel to each other as well as to the long axis 
of the stem. In the section of Eucalyptus exhibited this 
is not the case. The axes of the aggregated wood cells 
incline in one lateral direction and those of the vascular 
layer in an opposite one ; hence when a section of the stem 
of the tree is split vertically these two tissues are seen to 
dovetail obliquely into each other in a very singular manner. 
Professor Williamson also called attention to some recent 
discoveries throwing light upon the two rows of round or 
oval scars seen on the stems of the carboniferous genus Ulo- 
dendron. Mr. Carruthers long ago expressed his conviction 
that these scars marked positions from which serial roots 
had been given off. On the other hand Professor W. had 
pointed out (Phil. Trans. 1872, pp. 210 — 225) the extreme 
probability that these scars had supported cones or strobili 
— that conclusion having been based upon the peculiar 
manner in which the vascular bundles supplying the scars 
were given off from the central vascular cylinder of the 
branch or stem. Dr. Dawson of Montreal had arrived at a 
