536 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



and scarcely to be distinguished from that of ferns, with a true 

 indusium springing from a marginal vein. Lomaria has 

 pinnate forked veins. The sori and indusia are truly marginal. 

 The rhizoma very rarely forms a distinct caudex. Fteris is 

 scarcely different from Lomaria, except in the foliaceous fertile 

 pinnules and laciniae, narrower indusium, and fertile fronds 

 similar to the sterile ; whereas in Lomaria the fertile fronds 

 are narrower. Oampteria differs from Pteris in the lower 

 veins forming a distinct arc. Litobrochia has reticulate veins ; 

 Am,phiblestra strong, riblike veins, with reticulated interspaces. 

 In Allosorus the margin of the frond is re volute, and the sori 

 are covered by the crenato-plicate margin and indusium. To 

 this genus Pteris aquilina is referred by Presl. Platyloma 

 has oblong laterally confluent sori, so as to form a single broad 

 continuous marginal sorus. Cryptogramma scarcely differs from 

 Allosorus, to which genus Ceratodactylis is very near, but the 

 sori are longer, and the habit distinct. The sterile part of the 

 frond is like Osmunda, and the fertile part like Geratopteris, 

 consisting of contracted pinnae, with revolute indusiiform mar- 

 gins. Onychium is somewhat similar, but the frond is not 

 altered and contracted. Jamesonia has radiating free veins, 

 and round, confluent sori, forming one central sorus to each 

 pinna, the margin of which is revolute, and forms a common 

 indusium. In Cassebeera the sori are seated two together, 

 under each crenation of the frond, so that every spurious indu- 

 sium covers two sori. In Adiantwm the pinnse are mostly 

 trapezioid, and the veins are flabellato-pinnate. The genus is 

 close to Pteris, and often difficult to distinguish, and more by 

 habit than by character. Hewardia differs remarkably from 

 Adiantum in the reticulate venation. In Ochropteris the 

 sori are seated on the tips of from two to four converging vein- 

 lets, from which the indusium springs, and which form its base ; 

 whereas in Adiantum the sporangia are produced on the 

 under side of the indusium. Its habit is very peculiar. Chei- 

 lanthes has subgiobose distinct sori, and a narrow marginal 

 indusium, sometimes so narrow as to appear, at first sight, 

 deficient. The genus is with difficulty distinguished from 

 Adiantum, which passes into Gheilanthes by Ochropteris. 



