675 



XVIII. On Fossil Cycadean Stems from the Secondary Bocks of Britain 



By Wm. Carrutheus, Esq., F.L.S., F.G.S. 



(Plates LIV.-LXIII.) 1 



Read June 18th, 1868. 



THE organisms found in Palaeozoic rocks, referred by some authors to Cycadea, either 

 are so fragmentary that it is impossible to determine, with any approach to certainh, 

 their systematic position, or they belong to other orders of plants. The leaves that have 

 received specific names are imperfect fragments. The detached fruits present no charac- 

 ters justifying their reference to Cycadea. The stems from the Coal-measures, figured 

 and described by Presl 2 under the names Cycadites cokimnaris, C. mvolutxs, and Zamito 

 Cordai, are certainly arborescent cryptogams belonging to the same group as Lepido- 

 dendron, as Brongniart 3 and Miquel 4 have already shown. This is the position also oi 

 Guillard's Oycadium cy prinoph olis* ', from the Coal-measures of Eive de Gicr, in the centre 

 of Prance. Some uncertainty may be entertained regarding the Permian stems found m 

 Russia, and described by Eichwald 6 ; and yet a careful examination of the materials at my 

 command has satisfied me that their claims to be considered Cycadece cannot stand. Oi 

 the seven species, five are described from the impressions of the outer surface of the steins 

 preserved on the fractured surface of the rock, and only in the other two are then- ma 

 terials sufficient to show any traces of the form and structure of the stem 



In these tw 



(Temllaria antiqua and Diplodendron hastatum) there is a remarkable apP™ ch > '» "' 



arrangement of the parts, to Cycadece. It shonld be remembered, however, that .the Le 

 dodendroid fossils which abound in the later Paleozoic strata, and four of* e. • 

 described by Eichwald from the beds in which his supposed Cycads occur, had * d '« 

 parts entering into the structure of the stem arranged upon the same p an as n «**■ 

 In both, the vascular cylinder enclosed a ventral axis of more ***»**? ' VJ 

 was surrounded by a cortical cellular layer, through whrch the vascular hu s p. _ 



to the leave, l/some genera in both groups the leavessepara tf. y a, o, ^ = 



tioal layer, as in Cycas and Lepidodendron ; while in others a P°™ n ■ ^ 



« permanently atLhed to the stem, as in ^^^ "^ mimlt , 



withstanding this remarkable correspondence in the ai ian eme 



Thes 



uthfulness and power 



F 



expense was defrayed by 



\ssociatio 



»«nent at the disposal of the President and Council oi b« * J ^ ^ ^^ ^ the British Associat; 

 D r. Hooker. Many of the sections have been prepared by the he p o ^«^ ^ Dr Hooker 



inveshW,™ + u„ »^_i ™ * -o^;„ Th« others had been prepared io 



investigating the Fossil Flora of Britain. The 



Vorw 



' Tabl. Gen. Yeg. Foss. p. 59. *. } 



' Ann. des Sc. Phys. & Nat. d'Agricult. de Lyons, vol. n. p. 1« • 



Y '^. XXVI. 



Tiidschr. Nat. Wcten. v. *«» 



* Lethaa 



5 



