MATONIA-DIPTERIS SERIES 621 



show no regularity of position or of orientation, such as is seen in Matonia: 

 there is also an absence of any projecting receptacle. The sporangia of 

 the same sorus have been found to arise simultaneously in D. Lobbiana, 

 which may in this respect compare with Matonia. But in D. conjugata 

 they are formed successively, while those which appear later are distributed 

 without order amongst those first formed. The sorus, in this respect, 

 compares with that of the Mixtae, but the succession is not long main- 

 tained. When the individual sporangia are examined an essential 

 difference is found from the Polypodiaceous sporangium, with its vertical 

 ring ; for here the annulus is not only oblique, but also twisted : the series 

 of cells of the annulus can be traced laterally past the insertion of the 

 stalk, but the induration of their walls is interrupted at that point : the 



> 



FIG. 346. 



Dipteris conjugata, Rein. Portion of leaf, showing the extended surface, the webbing 

 between the pinnae, the venation, and the numerous sori spread over the surface. 

 Natural size. Figs. 344-346; after drawings by Mr. A. K. Maxwell. 



dehiscence is lateral, but there is no clearly defined stomium. The 

 sporangium itself is small, and the spore-output has been found both in 

 D. Lobbiana and in D. conjugata to approach the typical number of 64. 

 Comparing this sporangial' structure with that of other Ferns, it is actually 

 most like that of the Cyatheae, though the interrupted induration of the 

 annulus points a further departure from the primitive type, such as may 

 with reasonable probability be found in the sporangia of Matonia, and 

 ultimately of Gleic'henia. 1 



Turning to the anatomical characters, they bear out the above com- 

 parison ; for the rhizome contains a simple solenostele, while the leaf-trace 

 comes off as a single ribbon-like strand, opening a leaf-gap which soon 

 closes again. The margins of the petiolar strand curve inwards to form 

 the usual horse-shoe curve, which only breaks up at a point close below 



1 See Miss Armour, New Phytologist, 1907. 



