FOSSIL CONIFERZ. 165 
The Conifers are all arborescent, having numerous branches, 
which are in general disposed with much regularity. The 
_ leaves are commonly acicular or needle-shaped, narrow, and 
linear : in two or three genera, however, (Dammara, Podocar- 
_ pus,) the foliage departs remarkably from the ordinary type, 
_ the leaves being broad and flat. The structure of the stem, 
_ though in its general characters essentially exogenous (see 
_ Pilate IV. fig. 4),—that is, having a central pith, medullary 
_ rays, zones of vascular tissue, and concentric circles of growth, 
_ —differs in the almost entire absence of spiral vessels, and 
inthe peculiar modification of the radiating bands of woody 
_ fibre, which are made up of uniform longitudinal vessels, and 
run parallel with the medullary rays. The lateral walls of 
these vessels have longitudinal rows of areole, which are 
generally circular or elliptical, but when in contact are 
angular and polygonal: each areola has a small pore or 
punctation in the centre. These discs, glands, or ducts, as 
they are called, are variously arranged in different genera ; 
they are generally confined to the contiguous and corre- 
‘sponding lateral surfaces of the fibres; and occur rarely, if 
ever, on the inner and outer aspects of the vessels. In the 
recent genus Pinus the rows of ducts are single in some 
species ; in others both single and double series occur, but 
never more than two, and in the latter case the ducts are 
always parallel to each other (see pl. v. 3b. Wond. pp. 696, 
725). But in the Araucarie, or Norfolk Island Pines, the 
vessels have double, triple, and sometimes quadruple, rows 
of discs, of smaller size than in the common pines ; and in 
the double series, these bodies are always arranged alter- 
nately (Wond. p. 696. Bd. 56 a.); Mr. N me states that 
there are about 50 discs in the length of =, inch, the dia- 
meter of each not exceeding +;/,5 inch. 
The form and arrangement of these ducts, and the struc- 
ture of the medullary rays, are the characters on which the 
scientific botanist relies for the detection of the affinities of 
