DICTTOPHYLLTJM. 123 



Dictyophyllum rugosum, but in other species the sporangia are 

 described as having a complete vortical or oblique annulus and 

 tetrahedral spores. 1 ] 



In 1828 Brongniart proposed the name Phlelopteris Phillipsi for 

 the plant figured by Lindley & Hutton in 1834 as Dictyophyllum 

 rugosum ; the latter name is quoted by the French author as 

 a synonym, although the plant was not described in the Fossil 

 Flora until 1834. We must assume, therefore, that Brongniart 

 saw the description by the English authors some years before 

 Lindley & Hutton published their work. The name Dictyophyllum- 

 rugosum has been usually accepted, and, apart from the question 

 of strict priority, it is adopted as the better known and more 

 convenient designation. In a later work, Brongniart 2 expressed 

 the opinion that the English species should probably be referred 

 to Presl's genus Camptopteris. 



In 1856 Zigno instituted a new specific name, Dictyophyllum 

 Leckenbyi, for a Dictyophyllam frond from the Yorkshire coast, 

 with deeply pinnatifid pinnae having long and narrow ultimate 

 segments, which he regarded as distinct from D. rugosum. The 

 difference between such a leaf as that shown in pi. xxiii. of Zigno' s 

 work and Williamson's drawing published by Lindley & Hutton, 

 consists chiefly in the longer and narrower segments of the former, 

 but the existence of transitional forms affords ample evidence 

 of the specific identity of the two forms. In 1878 Nathorst 3 

 discussed at some length the genus Dictyophyllum, and quoted 

 the species as characterized by very variable leaves and as 

 illustrating the difficulty of distinguishing between species and 

 varieties. 



The relationship of Dictyophyllum rugosum with recent ferns 

 is of considerable interest. The genus Dictyophyllum has been 

 quoted as a leptosporangiate fern agreeing in certain characters 

 with both the Gleicheniacea) and CyathcaceoD, 4 and in that respect 

 comparable with Matonidium and Lnccopteris. Some of the more 

 perfect specimens of Dictyophyllum certainly suggest a comparison, 



1 Schenk (67), pi. xvi. 



2 Brongniart (49), p. *2. 



3 Nathorst (78 2 ), p. 13. 



4 Solms-Laubach (91), p. 154. 



