ig in early summer, when the
minute and tender cones, possessed of all the beauty of flowers, first
appear along its sides.

[Illustration: Fig. 132.]

[Illustration: Fig. 133.

ZAMIA.]

[Illustration: Fig. 134.

ZAMIA.]

Among conifers of the Pine and Araucarian type we mark the first
appearance in this system, in at least Scotland, of the genus Thuja. One
of the Helmsdale plants of this genus closely resembles the common Arbor
Vitae (_Thuja occidentalis_) of our gardens and shrubberies. It exhibits
the same numerous slim, thick-clustered branchlets, covered over by the
same minute, sessile, scale-like leaves; and so entirely reminds one of
the recent Thuja, that it seems difficult to conceive of it as the
member of a flora so ancient as that of the Oolite. But not a few of the
Oolitic plants in Scotland bear this modern aspect. The great
development of its Cycadaceae,--an order unknown in our Coal
Measures,--also forms a prominent feature of the Oolitic flora. One of
the first known genera of this curious order,--the genus
Pterophyllum,--appears in the Trias. It distinctively marks the
commencement of the Secondary flora, and intimates that the once great
Palaeozoic flora, after gradually waning throughout the Permian ages, and
becoming extinct at their close, had been succeeded by a vegetation
altogether new. At least one of the Helmsdale forms of this family is
identical with a Yorkshire species already named and figured,--_Zamia
pectinata_: a well marked Zamia which occurs in the Lias of Eathie
appears to be new. Its pinnate leaves were furnished with a strong woody
midrib, so well preserved in the rock, that it yields its internal
structure to the microscope. The ribbon-like pinnae or leaflets were
rectilinear, retaining their full breadth until they united to the stem
at right angles, but set somewhat awry; and, like several of the recent
Zamiae, they were striped longitudinally with cord-like lines. (Fig.
133.) Even the mode of decay of this Zamia, as shown by the abrupt
termination of its leaflets, exactly resembled that of its existing
congeners. (Fig. 134.) The withered points of the pinnae of recent Zamiae
drop off as if clipped across with a pair of scissors; and in fossil
fronds of this Zamia of the Lias we find exactly the same clipped-like
appearance. (Fig. 135.) Another Scotch Zamia (Fig. 136), which occurs in
the Lower Oolite of Helmsdale, resembles the Eathie one in the breadth
of its leaflet