232 GLOSSOPTEKIS AND ITS ALLIES, 



3. The structure of the Genus Glossopteris. 



The genus was founded by A. Brongniart, on fronds received 

 both from India and Australia, which he described as G. 

 hrowniana, var. indica, and var. australasica respectively.* It 

 includes simple petiolate leaves, varying in shape from elongately- 

 elliptical, oblong-elliptical, widely ovate, and spathulate to lingual- 

 lanceolate, and possessing a generally strong and frequently striate 

 mid-rib, sensibly attenuating upwards, and at times reaching the 

 apex, or even evanescing a short distance before attaining the top 

 of the leaf. The secondary veins emerge from the mid-rib usually 

 at an acute angle, and by frequent anastomosis form a very 

 characteristic, elongately-hexagonal network, extending over the 

 whole or only a portion of the frond. The fronds attain a large 

 size, for McCoy mentions those of G. hrowniana as six inches in 

 width, and probably reaching a length of two feet.f Brongniart 

 imagined that the reticulation of the secondary veins was confined 

 to near the mid-rib, but this erroneous view was corrected by 

 Morris,! who pointed out the distribution of the mesh at times 

 over the whole surface. 



Of such simple leaves has Glossopteris been supposed by all but 

 two writers to be composed, the existence of the so-called species 

 depending on the outline of the leaf and form of the net-venation. 

 It seems to have escaped the notice of subsequent writers that 

 Dana tiguredg a nuuiber of fronds of Glossoj)teris, believed to be 

 G. hrowniana var. australasica, attached in a clump to a fragment 

 of stem. Zigno expressed the opinion, so Bunbury states,|| that 

 this species had a compound or digitate frond, and quoted a report 

 that a specimen had been found to establish the fact. This, how- 



* Hist. V(^g. Foss. 1828, i. p. 223. 

 t Ann. Mag. Nat. Hist. 1847, xx. p. 151. 

 J Strzelecki's Pliys. Descrip. N. S. Wales, &c., 1845, p. 247. 

 § Willies, U.S. Explor. Exped. x (Geology), 1849, p. 716, Atlas, t. 12, 

 f. 13C. 



II Quart. Journ. Geol. Soc. 1861, xvii. p. 327. 



