Chemical evidence for separating the psilotaceae from the filicales.

The distribution of flavonoid compounds in Psilotum, Tmesipteris, and primitive filicalean ferns shows that it is unlikely the two groups are closely related. The Psilotaceae synthesize only amentoflavone and related biflavonyls which are totally absent from ferns. The primitive ferns contain the full complement of flavonols and proanthocyanidins, as found in all other filicalean families.