68 PROTOPTERIS. 
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 Cyatheacee. 
In Corda’s ‘‘ Flora der Vorwelt” eight genera, including Pro- 
topteris and Zempskya, are grouped together in the family 
Protopteridee. 
The genus Protopteris is thus defined by Corda, who consider- 
ably extends the earlier definition in Sternberg’s work! :— 
‘‘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. Radicule 
adventive per totam superficiem distribute. Cortex medullosa. 
Cylindrus lignosus clausus octangularis, angulis rotundatis. 
Liber externus in fasciculis anseeformibus disjunctis distributus, 
internus continuus ligno adnatus. Vagina vasorum tenuis. 
Lignum tenue, radiis medullaribus tenuibus vel nullis percursum ; 
vasis amplis sexangularibus scalareeformibus. 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*; but, failing more trustworthy evidence, the pattern 
of the leaf-trace is certainly a very convenient feature in the 
identification of fossil forms. Carruthers,? in his paper on a 
Lower Greensand Protopteris stem, is disposed to agree with 
Brongniart and: Goppert 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. 
