946 REPORT— IDOO. 



resemMe the corresponding strands in Lyginodendron Otdhammmm. The secondary 

 wood has narrow medullary rays, and quite resembles that of an araucarian 

 Conifer. 



The other species is identical with the Araucarioxylon antiquum described by 

 Witham. Here the pith is of large size, nearly an inch in diameter in the specimen 

 illustrated, and is surrounded by a ring of forty or fifty small primary xylem 

 bundles, mesarch in structure, whicb appear to have passed out into the leaves in 

 pairs. In this form the secondary wood has somewhat broad medullary rays, and 

 is so far less Coniferous in character than that of A. fasciculare. 



The interest of the two species described consists in their affording a link, so 

 far as the primary structure of the wood is concerned, between certain of the 

 Cycadofilices and the CordaitefB. 



The author is indebted to Mr. R. Kidston, F.G.S., for the loan of the specimens 

 on which the investigation is based. 



5. On the Structure and Affinities of Dipteris conjugata, Reimo., ivith Notes 

 on the Geological History of the DijJteridimK. By A. C. Seward, F.R.S., 

 and Elizabeth Dale. 



For the material used in the anatomical investigation of Dipteris conjugata the 

 authors are indebted to Mr. Shelford, of the Sarawak Museum, Borneo, and to 

 Mr. Yapp, of Caius College, Cambridge. The genus Dipteris is represented by 

 four recent species : D. conjugata, Reinw. [ = I'oh/podium {Dijyteris) HorsfieldH, 

 R. Br.], D. WaUichii, R. Br., D. Lobbiancc, Hk., and D. quinquefurcata, Baker ; 

 of these D. Wallichii occurs in tlie subtropical regions of Northern India, the 

 other three species being characteristic of the Malayan region. Among Mesozoic 

 ferns the genera Protorhipis, Dictyophyllmn, Camptopteris afford examples of extinct 

 tj'pes closely allied to Dijiferis, and widely spread geographically during the 

 Jurassic epoch. 



The authors propose to separate the recent genus and the fossil forms from the 

 Polypodiacese and place them in a distinct family — the Dipteridinre. The sporangial 

 characters of Dipteris do not conform precisely to those typical of the Polypodiacese, 

 and the anatomical features afford additional evidence in favour of placing Dijiteris 

 in a special subdivision of the Leptosporangiate ferns. 



The stem of Dipteris conjugata possesses a single annular stele in which 

 the protoxylem strands occupy a central (mesarch) position. The proto- 

 phloem elements are sharply marked off from the rest of the phloem, which 

 is succeeded by a pericycle 3-4 cells in width ; a distinct endodermis encloses the 

 stele both internally and externally. Immediately behind each leaf the annular 

 stele of the stem becomes elongated in a vertical direction, and gives ofl' an inverted 

 U-shaped branch which ascends obliquely upwards into the leaf-stalk. The foliar 

 gap, left after the passing off of the meristele, closes up in front of the leaf, and the 

 stele resumes its normal tubular form. 



The paper deals also with the structure of the roots, leaves, and sporangia of 

 Dipteris conjugata, the comparison of the anatomical features with those of tie 

 Cyatheacese and other ferns, and conclude.'; with an account of the geological and 

 geographical range of such fossil ferns as may reasonably be placed in the family 

 Dipteridinte. 



6. Ilhistrations of Sand-binding Plants, By Professor F. 0. Bower, F.R.S. 



