XXV] ZYGOPTEREAE 447 



1*5 — 2 cm. From the antennae a pair of small bundles is 

 given off alternately from the right and left side, as in 

 Zygopteris; the members of each pair coalesce after leaving 

 the antennae and then separate to pass into the lateral 

 branches of the frond. The position of the protoxylem and 

 the formation of the lateral xylem strands previous to their 

 separation are shown in fig. 308, C. On the side of the 

 vascular strand shown in fig. C, 2, the two lateral extensions 

 of the antennae are converging towards one another previous 

 to their separation and subsequent union. The ovoid sporangia 

 occur in groups of three to six and are coalescent below with a 

 central receptacle ; they have no annulus, but the cells on the 

 side next the receptacle are smaller than those on the external 

 wall (fig. 309, A). The synangial form of the sorus suggests 

 comparison with Marattiaceae. 



The species described by Renault from the Culm of Esnost 

 is regarded by P. Bertrand as identical with that described by 

 Solms, from the Culm of Falkenberg, as Zygopteris Roemeri^. 

 Diplolahis is compared by P. Bertrand with Metaclepsydropsis, 

 the generic name given to the Lower Carboniferous petiole 

 described by Williamson as Rachiopteris duplex^. 



Mr Gordon has recently described in a preliminary note a 

 new type of stem stele under the name Zygopteris pettycurensis 

 from the Lower Carboniferous plant bed of Pettycur' : he regards 

 the petioles attached to the stem as identical with Zygopteris 

 Roemeri Solms-Laubach*. This species, founded by Solms- 

 Laubach on petioles only, is placed by Bertrand^ in the genus 

 Biplolahis and regarded as identical with D. esnostensis Ren. 

 The stele found by Mr Gordon may therefore be assigned to the 

 genus Diplolahis : it includes two regions composed exclusively 

 of tracheae and is cylindrical in transverse section. The inner 

 xylem zone consists of short, square-ended, reticulately pitted 

 elements and the outer zone is composed of long and pointed 

 conducting tracheae. The scalariform protoxylem elements are 



1 Solms-Laubaoh (92). ^ Williamson (74) A. Pis. liv. lv. 



3 Gordon (09). Mr Gordon's more complete account of tijis plant will 

 shortly be published. I am indebted to him for furnishing me with the 

 main facts in regard to the anatomical features. 



* Solms-Laubaoh (92) PI. ii. fig. 13. » Bertrand, P. (09) p. 211. 



