No conifer grows in Denmark except under careful cultivation, which, however, is largely practised in Jutland.
In those stems which have been referred with certainty to the Cordaiteae there is no centripetal wood; the spiral elements are adjacent to the pith, as in a recent Conifer or Cycad; certain stems, however, are known which connect this type of structure with that of the Lyginodendreae; this, for example, is the case in the Permian genus Poroxylon, investigated by Bertrand and Renault, which in general structure has much in common with Cordaiteae, but possesses strands of primary wood, mainly centripetal, at the (After Grand' Eury, modified.
In diameter; the wood, however, was dense, and had the structure of that of an Araucarian Conifer; specimens of the wood have accordingly been commonly referred to the genus Araucarioxylon, and at one time the idea prevailed that wood of this type indicated actual affinity with Araucarieae.
The first species of the genus, Nematophycus Logani, was discovered by Dawson in 1856 in the Lower and Middle Devonian of Canada, and was described by him as a Conifer under the name of Prototaxites.
Woody or lignified cell-walls appear to contain substances called conifer-in and vanillin, in addition to various other compounds which are imperfectly known.
Coniferales: " Report of the Conifer Conference " (1891) Journ.
This genus has long been known as a common and widely spread Jurassic and Cretaceous conifer, but owing to the absence of petrified specimens and of well-preserved cones, it has been impossible to refer it to a definite position in the Coniferales.
Other seams are full of the twigs and cones of Athrotaxis, a Conifer now confined to Tasmania.
A wellknown fossil conifer from Triassic strata - Voltzia heterophylly - also illustrates a marked dissimilarity in the leaves of the same shoot.
Above the sea, the limit of the luxuriant growth of that hardy conifer in Britain; and in moist valleys or on imperfectly drained acclivities Norway spruce is more suitable.
The primary vascular bundles in a young conifer stem are collateral, and, like those of a Dicotyledon, they are arranged in a circle round a central pith and enclosed by a common endodermis.