Abundant secondary growth occurs from a bifacial vascular cambium . Tracheids of many conifers have a characteristic circular bordered pitting on element walls. Recall that this feature is not restricted to conifers, but has been useful for distinguishing conifer from other wood taxa in permineralized specimens. As the name implies, the conifers are called conifers because they have cones. As with other strobili we have studied, those of conifers are derived from sporangia-bearing branch systems that have been modified.
Extant conifers are most monecious but have differentiated mega- and microsporangiate cones.
It is in the ovule-bearing structures that the homology with Cordaites is best expressed. With this interpretation, the entire axis of ovuliferous Cordaianthus can be modified without major rearrangement into the conifer seed cone. Florin argued, therefore, that Cordaites may be the ancestor to the conifers. Florin's homologies seem generally sound, but his evolutionary interpretation is still a topic of debate. You'll note that in the overall phylogeny used to organize the Virtual Paleobotany Laboratory, we leave the node linking Cordaites, Ginkgo and conifers unresolved to express that there is disagreement among current workers and still more research to be done.