68 PEOTOPTEEIS. 



Genus PROTOPTERIS, Presl. 

 [Sternberg, Flora der Vorwelt, Heft vii. 1838, p. 169.] 



This generic name was applied by Presl to a tree-fern stem 

 which he had previously figured and described as Lepidodendron 

 punctatum '> the plants which he included under Protopteris are 

 compared to living members of the Cyatheacece. 



In Corda's " Flora der Vorwelt" eight genera, including Pro- 

 topteris and Tempskya, are grouped together in 'the family 

 Protopteridece. 



The genus Protopteris is thus defined by Corda, who consider- 

 ably extends the earlier definition in Sternberg's work 1 : 



" Caudex arboreus, extus nudus vel radiculis adventivis 

 involutus. Cortex pulvinulis foliorum quaternariis spiraliter 

 positis oblongis ornata; cicatricibus foliorum medio depressis, 

 fasciculo vasorum centrali simplici hippocrepico continuo decoratis, 

 et infra fasciculis rotundis minutis disjunctis 6 vel 8, et supra 

 fasciculis sequalibus lateralibus vel nullis circumdatis. Eadiculae 

 adventiva3 per totam superficiem distribute. Cortex medullosa. 



Cylindrus lignosus clausus octangularis, angulis rotundatis. 

 Liber externus in fasciculis ansa3formibus disjunctis distributus, 

 internus continuus ligno adnatus. Vagina vasorum tenuis. 

 Lignum tenue, radiis medullaribus tenuibus vel nullis percursum ; 

 vasis amplis sexangularibus scalaraBformibus. Medulla centralis 

 ampla, parenchymatosa." 



The most readily recognized characteristic of the genus is the 

 horse-shoe form of the leaf-trace, as seen on the surface of the 

 petiole scars. Schenk points out that such a character as this 

 cannot be regarded as very reliable in the determination of tree- 

 fern stems 2 ; but, failing more trustworthy evidence, the pattern 

 of the leaf-trace is certainly a very convenient feature in the 

 identification of fossil forms. Carruthers, 3 in his paper on a 

 Lower Greensand Protopteris stem, is disposed to agree with 

 Brongniart and Go'ppert in attaching considerable importance to 

 the form of the petiole bundle. 



1 Flor. Vorwelt, p. 76. 



2 Foss. Pflanz. p. 46. 



3 Geol. Mag. 1865, p. 484. 



