History of Monocotyledons. 209 
In the pinnae of the Mesozoic Cycad Ctenis , which in some 
species attain a considerable breadth 1 , the parallel veins are 
united here and there by oblique cross-connections, thus 
closely simulating certain types of monocotyledonous leaves. 
The superficial resemblance between a palm-leaf, such as 
Calamus ciliaris , Blume, and the frond of a Cycad, would not 
readily mislead the practised eye of a botanist, but with this 
form of leaf imperfectly preserved on a piece of sandstone or 
shale, such a mistake might easily be made. It is not to be 
wondered at that the older palaeobotanists referred Unger’s 
genus Cordaites to the Palms. Schenk 2 has remarked that 
we do not know at what date Cordaites became extinct, and it 
is quite possible that some of the so-called monocotyledonous 
leaves should be referred to this genus. Nathorst 3 has 
demonstrated how the impression of a drifted seaweed on the 
surface of fine sand may simulate parallel venation. The 
impression of a radial section of a woody stem of homogeneous 
structure, such as a Conifer, may be misleading, unless we are 
able to detect the cross-lines of cells forming the medullary 
rays. Flattened and imperfect stems of equisetaceous plants, 
e. g. Equisetites and Schizoneura , and indeed the leaves of 
the latter, may well be confounded with angiospermous leaves. 
Sufficient examples have been cited to illustrate the need of 
caution, and other instances are supplied by the examples 
dealt with below. 
Palaeozoic and Mesozoic ‘ Monocotyledons.’ 
Pothocites. The specimen described many years ago by 
Paterson 4 under this name, was referred to by Williamson 5 
1 E. g. those figured by Raciborski in Flora Kopalna-Kracow, 1894, Pis. XVI, 
XVII, and XVIII. 2 Die fossilen Pflanzen, p. 200. 
8 Om nagra formodade Vaxtfossilier. [Ofversigt Kongl. Vet. Akad. Forhand. 
1873, No. 9]. Pis. XV and XVI. See also, Kongl. Svensk. Vetenshaps-Akad. 
Hand. Vol. xviii, No. 7, 1880, Pis. IX and X. 
4 Trans. Bot. Soc. Edinburgh, Vol. i, 1844, p. 45, PI. III. 
5 Anomalous Oolitic and Palaeozoic forms of vegetation, 1883, p. 11, Fig. 9. 
