J. SMITH ON THE GENERA OF FERNS. 165 



R. Br. 6. P. serrulata, Linn. 7. P. beterophylla, Sw. 8. 

 P. irregularis, Kaulf. 9. P. pungens, Willd. 10. P. biauri- 

 ta, Linn. 11. P. arguta, Vahl. 12. P. iiirsuta, (Lonchitis, 

 Linn.) 13. P. tremula, 7i. Br. 14. P. esculenta, /^ors/. 15. 

 P. candsLia^ Linn. 16. P. aquilina, Li7in. Illust. Schk. crt/pt. 

 t. 88. Hook, et Grev. Ic. Fil. t. 130. Hook. Gen. Fd. t. 

 64. A. 



Obs. The original character of this genus as given by 

 Linneeus, Swartz, and others, consisted in the .sporangia 

 being situated in the axis of an exterior attached lateral in- 

 dusium, constituting a linear marginal sorus, which character 

 would now embrace above 150 known species; but, by adopt- 

 ing a few other points of structure, we have been enabled to 

 divide that number into several generic groups characterized 

 under Cassebeera, Platyloma, Doryo})teris, Litobrochia, and 

 Pteris, as now here characterized, and which still contains the 

 greatest number of species. 



Presl separates the Pteris aquilina of Linnaeus and its as- 

 sociates from this genus, and places them under his genus 

 Allosorus, which must be confessed is composed of rather 

 a heterogeneous mass of species, not only of distinct habits, 

 but also differing in other important characters, which 

 render the adoption of the genus so constituted inadmis- 

 sible. Some observers have stated, that the sori of Pteris 

 aquilina are furnished with a narrow indusium, situated on 

 the inner side of the receptacle, but from my observation, 

 I cannot consider the slightly elevated fimbriate ridge which 

 bounds the inner side of the sporangia as being analogous 

 to an indusium. And although the group of which P, 

 aquilina is the type, is somewhat different in habit from 

 the rest of the genus, yet I do not find sufficient character to 

 allow them to be considered otherwise than as constituting a 

 group of this genus under the sectional name Orniihopteris of 

 Agardh. 



61. Onychium, Kaulf. 



(Leptostegia, D. Don. Alosorefe sp. Presl.) 

 Veins simple direct, free, or their apices combined by a 



