No doubt some of the fossils from the Silurian and Cambrian rocks are true algae, and Nathorst has pointed out that such a species as Hall’s _Sphenothallus angustifolius_[243] may well be an alga. Additional examples might be quoted from Bornemann and other writers, but in view of the attempts which are sometimes made to trace the development of more recent plants to more than doubtful Lower Palaeozoic Algae, one must agree with Nathorst’s opinion,—“Je crois que l’on rend un bien mauvais service à la théorie de l’évolution, en essayant de baser l’arbre généalogique des algues fossiles sur des corps aussi douteux que les Bilobites, Crossochorda, Eophyton, etc.[244]” There are many carbonaceous impressions on rocks of different ages which it is reasonable to refer to algal origin, and although such are of little or no botanical value, it may be a convenience to refer to them under a definite term. The comprehensive generic name _Algites_[245] has been suggested as a convenient designation for impressions or casts which are probably those of algae. [Sidenote: SUPPOSED FOSSIL ALGAE.] Some of the fossils described by Mr Kidston from British Carboniferous rocks as probably algae present an undoubted algal appearance, and might be placed in the genus _Algites_; but in some cases—e.g. _Chondrites plumosa_[246] Kidst. from the Calciferous Sandstone of Eskdale, one feels much more doubtful; in this particular instance the impressions suggest the fine roots of a water-plant. The statement is occasionally made that the numerous fossil algae and the absence of higher plants in the older strata justify the description of the oldest rocks as belonging to the ‘age of algae.’ Such an assertion rests on an unsound basis, and is rather the expression of what might be expected than what has been proved to be the case. The oldest plants with which we are at all closely acquainted are of such a type as to forcibly suggest that in the lowest fossiliferous rocks we are still very far from the sediments of that age which witnessed the dawn of plant life. Many of the obscure markings on rock surfaces which have been referred to existing genera of algae or described as new genera, are much too doubtful to be included even under such a comprehensive name as _Algites_. Space does not admit of further reference to determinations of this type which abound in palaeontological literature.