v] FERNS 89 



The exposure by a stroke of the hammer, on the 

 fractured surface of a rock picked up on the beach 

 at Hayburn Wyke (a few miles south of Whitby), of 

 a piece of fern frond which is unmistakably closely 

 allied to the species described by Wallace on Mount 

 Ophir, establishes a link between the Jurassic and 

 the present era and presents a fascinating problem in 

 geogi^aphical distribution. These fossil Matonias are 

 known to students of ancient plants as species of 

 the genus Matonidium, a name adopted by a German 

 botanist for specimens apparently identical with those 

 from the Yorkshire coast discovered in slightly younger 

 rocks (Wealden) in North Germany. The same type 

 has been found also in sediments of Wealden age on 

 the Sussex coast. Other leaf-impressions agreeing 

 closely with those of Matonidium have been obtained 

 from the Yorkshire Jurassic rocks and these are 

 assigned to another genus Laccopteris, an extinct 

 member of the family Matonineae. It is not merely 

 in the habit of the fronds and in the shape and 

 venation of the leaflets that these fossil ferns resemble 

 the existing species, but the more important features 

 exhibited by the spore-capsules supply additional evi- 

 dence. It has already been pointed out that the stems 

 of Matonia are characterised by a type of structure 

 unknown in an identical form in any other recent fern. 



A few years ago Prof. Bommer discovered frag- 

 ments of leaves and stems in Wealden beds a few 



