Considering the soft nature of the body of recent Liverworts, it is not surprising that they are poorly represented in a fossil state. In the absence of the sexual reproductive organs, or of the sporophytes, which have scarcely ever been preserved, exact identification is almost hopeless. The difficulties already referred to in dealing with the algae, as regards the misleading similarity between the form of the thallus and the bodies of other plants, have to be faced in the case of the Liverworts. Many of the thalloid Liverworts, if preserved in the form of a cast or impression without internal structure or reproductive organs, could hardly be distinguished from various genera of algae in which the thallus has the form of a forked plate-like body. Such genera as _Pellia_, _Marchantia_, _Lunularia_, _Reboulia_, and others bear a striking resemblance to _Fucus_, _Chondrus_ and many other algae. Imperfect specimens of certain Lichens, not to mention some of the Polyzoa, might easily be mistaken for Liverworts. Among the higher plants, there are some forms of the _Podostemaceae_ which simulate in habit both thalloid and foliose Liverworts as well as Mosses[450]. The members of this Dicotyledonous family are described as water-plants with a Moss- or Liverwort-like form; they occur on rocks in quickly-flowing water in the tropics. In one instance a recent Podostemaceous genus has been described as a member of the Anthocerotales; the genus _Blandowia_[451], referred to by Willdenow as a Liverwort, has since been recognised as one of the _Podostemaceae_. The resemblance between some of the foliose _Hepaticae_ and genera of Mosses is often very close. In certain Mosses, such as _Hookeria pennata_[452], the large two-ranked leaves suggest the branches of a _Selaginella_. [Illustration: FIG. 48. A. _Tristichia hypnoides_ Spreng. From a specimen in the British Museum. B. _Podocarpus cupressina_ Br. and Ben. (After Brown and Bennett[453].) C. _Selaginella Oregana_ Eat. From a plant in the Cambridge Botanic Garden. A, B and C very slightly reduced.]