XXI I] DISCOPTERIS 403 



species are of oval-triangular form, 5 — 15 mm. long and 

 2'5 — 6 mm. broad\ An examination of the type-specimens 

 of Discopteris from Vienna enabled Zeiller to correct Stur's 

 original description of the sori : he found that the Austrian 

 and French specimens, though specifically distinct, undoubtedly 

 belong to one genus. The sori in Discopteris cristata are 

 globular, as in the recent genera Cyathea and Alsophila, and 

 frequently cover the whole face of the lamina. The individual 

 sporangia are 0"4 — 0"5 mm. long and 0"15 — 0'2 mm. in diameter; 

 they are exannulate, but for the annulus is substituted a group 

 of thicker- walled and larger cells in the apical and dorsal region. 

 The description by Stur of a hemispherical receptacle seemed 

 to indicate an important difference between the Austrian and 

 French species; but Zeiller found that this feature does not 

 actually exist and that it was so described as the result of 

 misinterpretation. Zeiller succeeded in isolating spores, 40 — 50 /* 

 in diameter, from some of the sporangia of D. cristata and 

 found that they exhibited the three-rayed pattern characteristic 

 of fern-spores and which is indicative of their formation in 

 tetrads. The conclusion arrived at is that the genus Discopteris, 

 as represented by D. karwinensis, D. cristata etc., may be 

 regarded as a true fern and included in the Marattiaceae. As 

 Zeiller points out, the sori of Discopteris differ from those of 

 recent Marattiaceae in their pluriseriate construction and 

 agree in this respect with those of the Cyatheaceae. The 

 comparison already made'' between the sporangia of D. Rallii 

 and those of recent Osmundaceae holds good : the genus 

 affords another example of a generalised type, in this case 

 probably a fern, combining features which are now distributed 

 among the Marattiaceae, Osmundaceae and Cyatheaceae. 



In addition to genera founded on true synangia or groups 

 of free or partially united sporangia, the literature of Palaeozoic 

 ferns contains several generic names applied to sporangia which 

 occur singly on Sphenopteroid or Pecopteroid pinnules. The 

 following may serve as examples ; but it should be stated that 

 these will probably be transferred eventually to the Pterido- 

 1 Renault and Zeiller (88) A. PI. xxiv. " page 325 



