440 Mr. A. Mallock. 



parenchyma ; an endodermis and pericycle surround each stele, and in 

 the case of the annular steles these layers occur both internally and 

 externally. At the nodes the outer annular stele bends up into the 

 leaf-stalk, and a branch is also given off' from the margin of a gap 

 formed in the inner annular stele ; the axial vascular strand may or 

 may not be in continuity with the meristele of the leaf. The petiole is 

 traversed by a single stele, similar in shape to that of certain Cyathe- 

 aceous ferns ; towards the top of the leaf-stalk the stele alters its form, 

 and gradually gives off separate U" sna P e( ^ branches to supply the 

 pinnae. 



The most interesting feature in the structure of the pinnules is the 

 marked papillose form of the lower epidermal cells. The roots have a 

 triarch stele enclosed by a few layers of thick brown sclerous cells. 



In structure Matonia pectinata presents points of agreement with 

 several families of ferns, on the whole approximating more closely to 

 Cyatheacese than to any other family ; but the peculiarities are such 

 as to fully confirm the conclusion previously drawn from external 

 characters that Matonia should be placed in a separate division of the 

 Filices. 



After comparing the structure of the Malayan species with that of 

 other fern genera, the paper concludes with an attempt to give an 

 account of the geological history of the Matoninese. The genera 

 Laccopteris and Matonidium are dealt with at some length, and 

 reference is made to other Mesozoic ferns, which may probably be 

 included in the same group. 



The data furnished by an examination of palseontological evidence 

 lead to the conclusion that in Matonia we have a survival of a family 

 of ferns, now confined to a few localities in Borneo and the Malay 

 peninsula, and represented by two living species, which in the Mesozoic 

 epoch had a wide geographical range, being especially abundant in the 

 European area. 



" Note on a new Form of light Plane Mirrors." By A. MALLOCK. 

 Communicated by LORD EAYLEIGH, F.B.S. Eeceived February 

 28, Read March 9, 1899. 



Having recently, in the course of some experiments on air waves, 

 had occasion to make use of some very thin films as coverings for the 

 openings of resonators, it occurred to me that such films, if stretched 

 over rings with edges ground to a true plane, might be used as plane 

 mirrors, and the following note records the results of the trials made 

 with this object in view. 



The best films were obtained by letting a few drops of a solution of 

 pyroxyline in amyl acetate spread on the surface of water and lifting 



