CORDAITEAE. 105 



doubtful of objects and were mixed up with Noggerathiae, are now the 

 best-known of all classes of fossil plants which are no longer included in 

 our present vegetation. 



The leaves of Cordaiteae are simple, sessile, elongate-elliptical or 

 ribbon-like from a contracted base, and rounded or acute at the ex- 

 tremity. They are in all cases traversed by conspicuous parallel nerves 

 which lie very close to one another, and according to Grand' Eury are oc- 

 casionally forked. Differences appear to have been observed in the size of 

 the nerves, but we must be careful how we make use of this character, 

 since it depends a good deal on the mode of preservation. Usually all 

 the nerves are of the same size, or they gradually increase in size towards 

 the middle of the leaf; more rarely stronger and weaker nerves alternate 

 regularly, as, for example, in Cordaites principalis, Gein., in which Grand' 

 Eury finds four weaker nerves between every two stronger nerves. This 

 observer has divided the entire group of Cordaiteae into three genera 

 founded on the form of the leaves, but these must be regarded as entirely 

 provisional so long as their relation to the flowers which have been dis- 

 covered is not better known than it is at present. These genera are Dory- 

 cordaites, with leaves which may be fifty centimetres in length and which 

 narrow gradually into an acute apex ; Poacordaites, in which also the leaves 

 may be half a metre in length ; but are linear and grass-like and are suddenly 

 rounded off to an obtuse termination ; and Cordaites, with shorter obovate 

 or spathulate obtuse leaves which are sometimes incised. The Poacordaitae, 

 which are chiefly found at St. Etienne in different beds from the other two 

 types, have been recently separated from them by Renault 1 and placed 

 with Taxineae. I am not informed respecting the reasons which have 

 determined him in this matter. 



Leaves of Cordaites are extraordinarily abundant in the black pebbles 

 of Grand' Croix. In some fragments, such as one for which I am indebted 

 to Renault's kindness, large numbers of the leaves lie in layers one above 

 another like damp beech-leaves on the ground in our forests. In these 

 specimens the structure is often well preserved, and the distribution of the 

 tissues displays a surprising multiplicity of detail considering the uniformity 

 of shape. Unfortunately the silicified leaves come under our observation in 

 fragments only, and it is impossible to refer them with any certainty to the 

 different species which have been determined from the impressions. Renault 

 has therefore marked all the transverse sections which he has named with 

 a note of interrogation ; and Grand' Eury has given special specific names 

 founded solely on the anatomical structure to the forms which he has ex- 

 amined. All the leaves which have been carefully studied, with the exception 

 of one kind only, show a simple layer of parallel vascular bundles running in 



1 Renault (2), vol. iv. 



