XXVIl] GLOSSOPTERIS 497 



most cases the lamina extends as a narrow margin to the leaf-base, but in 

 a few forms there is a short petiole (fig. 334). Though usually spathulate, 

 the frond may be linear-lanceolate, or ovate ; the apex is sometimes acute. 

 Leaves vary in length from 3 to 40 cm. and may in larger forms have a 

 breadth of 10 cm. Numerous lateral veins curve upwards and outwards 

 to the margin of the lamina or pursue a straight course almost at right- 

 angles to the midrib, (ii) Scale-leaves^ which diflPer from the foliage-leaves 

 in their much smaller size and in the absence of a midrib ; they are deltoid, 

 oval or cordate in shape and generally terminate in an acute apex; the 

 edge of the lamina may be slightly incurved so that the leaf presents a 

 convex upper surface supplied with anastomosing veins. The scale-leaves, 

 which viiry in length from about 1 to 6 cm., probably acted as sporophylls. 

 The only evidence as to the nature of the fructification so far obtained 

 is represented by empty sporangium-hke organs (1-2 — 1-5 mm. long by 

 0-6 — 0-8 mm. broad) frequently associated with the scale-leaves 2. 



The leaves, in some cases at least, were borne near together on a 

 cylindrical stem or rhizome which produced branched adventitious roots '. 

 The fossils long known as Vertebraria were recognised by Zeiller* and by 

 Oldham* as the stems of Glossopteris. 



The systematic position of Glossopteris must for the present 

 be left an open question. Though usually spoken of as a fern, 

 it is noteworthy that despite the enormous abundance of its 

 foliage leaves in the Permo-Carboniferous strata of India, 

 Australia, South Africa, and South America, no single example 

 has been discovered which shows undoubted remains of sori 

 or sporangia. Many authors have described fertile leaves of 

 Glossopteris ; but it was not until Arber's discovery of sporangia 

 in close association with the scale-leaves that any light was 

 thrown on the nature of the reproductive organs. 



The probability is that Glossopteris was not a true fern but 

 a member of that large and ever-increasing class, the Pterido- 

 sperms. This opinion is based largely on negative evidence. 

 Such sporangia as have been described may have contained 

 microspores and the plant may have been heterosporous. The 

 occurrence of seeds in association with Glossopteris fronds 

 recorded by more than one writer^ though by no means 

 decisive and possibly the result of chance association, is favour- 



1 For figures see ZeiUer (96) A. ; Zeiller (02), (03) ; Arber (05) ; Seward (97) A. 



•^ Arber (05^) ; Seward (07"). ^ Bunbury (61) PI. xi. 



* Zeiller (96) A. ^ Oldham (97) ; Zeiller (97"). 



« Seward (97) A. (07=) ; Arber (02^) p. 20; Zeiller (96) A. p. 374. 



