14 



BRITISH EOCENE ELOEA. 



Order— CYCADACE^. 



These are palm-like Gymnosperms with usually unbranched stems, often marked with 

 lozenge-shaped leaf-scars, and bearing parallel-veined, hard, pinnate leaves. The wood 

 is soft and pith-like, with the characteristic gymnospermous structure. The seeds are hard 

 and woody, and borne on the edges of modified leaves, or in large cones, which are either 

 sessile or pedunculate. They are generally low shrubs, but occasionally reach a height 

 of thirty feet. They possess the general aspect of Palms combined with the fruit of 

 the Coniferap. There are two tribes, Cycade^ and Encephalarte^, with nine genera, 

 and from 75 to 100 species, inhabiting intertropical or subtropical America, Asia, 

 Australia, and the Cape. 



Eor many years Cycads were believed to occur in the Carboniferous, but later 

 investigation has not confirmed these views. They abounded in England during the 

 Jurassics ; and excellent illustrations of them are to be seen in Buckland's ' Bridgewater 

 Treatise,' the ' Transactions of the Geological Society,' 2nd ser., vol. iv, and in Lindley 

 and Hutton's ' Eossil Elora.' Carruthers has also published a monograph " on the 

 Eossil Cycadean Stems from the Secondary Bocks of Britain," in which all the species are 

 redescribed and figured.^ They have also been met with in the Jurassic of Spitzbergen, 

 and in great quantities in the Cretaceous Komeschichten of Greenland. They seem to 

 become rare in the Newer Cretaceous of Atane, and disappear altogether in the Arctic 

 Tertiaries. They migrated apparently from temperate Europe and America during the 

 Tertiary Periods, and the few supposed remains of them found hitherto in the Tertiaries 

 are in an unsatisfactory state of preservation.^ None are known in our Eocenes. 



Order— CONIFERiE. 



The Coniferse form by far the most extensive of the Gymnospermous orders. As at 

 present constituted, it consists of hard-wooded trees or shrubs, of exogenous growth, and 

 with polycotyledonous embryos ; but their woody structure is marked by discs, a 

 peculiarity which renders it easily recognisable in almost every state of preservation. 

 Their spiral vessels also are limited to the medullary sheath. They are both dioecious 

 and monoecious ; the female flower being either in cones or solitary, and the male 

 flowers usually in deciduous catkins, composed of a number of scales, in the body 



1 ' Trans. Linn. Soc.', vol. xxvi, p. 6/5, 1870, (read June 18th, 1868). This appears by far the most 

 important contribution to the history of Fossil Cycads, and is illustrated by ten very beautifully drawn 

 plates. M. Renault, ' Cours de Botanique Fossile, Premiere annee,' Paris, G. Masson, 1881, devotes the first 

 six chapters to fossil Cycadacese. 



2 These are — a small fragment from the Miocene of Svritzerland, nsLvaed Zamites tertiarius, Heer; 

 two fragments from Gelinden, named Z. palceocenicus, Saporta and Marion ; a cycadaceous leaf and indis- 

 tinct cone from Bonnieux, and the Encephalartus from Koumi, in Euboea. 



