PHriJciiEs. 153 



Had the specimen been found in rocks known to contain tte 

 Temains of Angiosperms, there would be no hesitation in identifying 

 it as the leaf of a Dicotyledon; but seeing that we know of no 

 undoubted Angiospermous fossil in Jurassic strata, it is of the utmost 

 importance to demand satisfactory evidence before identifying a 

 plant, or fragment of a plant, as an Angiosperm. 



The statement made by Professor Bessey that " Monocotyledons 

 and Dicotyledons probably appeared at about the same time early 

 in the Mesozoic or late in the Palaeozoic "Ms founded on specimens 

 that have been referred to the Angiosperms on evidence that is 

 •entirely without value. It has been stated by Deane ' that well- 

 developed Dicotyledons occur in the Oxley beds of Australia, which 

 are regarded as Jurassic ; but I have not seen any figures in support 

 of this announcement, and in the absence of more data we cannot 

 attach much importance to the statement. Two imperfectly pre- 

 served fragments of leaves have been figured by Kurtz from the 

 Lias of South America '' as doubtful fossils resembling Dicotyledons ; 

 they may perhaps represent portions of a Bictyophyllum frond ; 

 they are at all events valueless as evidence in support of the 

 existence of Liassic Angiosperms. 



There is no doubt that some of the supposed earliest Dicotyledons 

 described from Portuguese rooks* are fronds of ferns similar in 

 form and venation to the orbicular 'mantel-leafs* of the recent 

 epiphytic fern Platyoerium : in the present case it is difficult to 

 believe that we have to do vsdth the leaf of a fern. The genus 

 Onetum — the sole living representative of the Gnetales, a section 

 of Gymnosperms — is characterised by leaves of the Dicotyledonous 

 type, and there is always the possibility to be borne in mind that 

 some of the so-called fossil Dicotyledons may be the leaves of 

 Gnetum. So far as it is possible to base an opinion on the im- 

 perfect specimen before us, the venation characters do not conform 

 closely to those of the leaves of recent species of Gnetum. 



As regards the geological age of the fossil, the impression 

 shown in Fig. 6, PI. XI. is entered in the Museum Eegister as 



' Begsey (97), p. H. 



2 Deaae (97), p. 858. 



3 Kurtz (01), pi. iii. figs. 10-U. 



* Saporta (94) ; Ward (95), (96). 



