APRIL. 



101 



The Aspleniece comprise fourteen genera, separable into three sets in 

 the following order : — With the indusia single and distinct — Actini- 

 opteris, Asplenium, Athyrium, 

 with free veins ; T/iamnopteris, 

 with the veins combined ; He- 

 midictyon, Allantodia, and 

 Ceterach, with the veins re- 

 ticulated. With the indusia 

 connivent in pairs face to face — 

 Scolopmdrium, with free veins ; 

 Antigramma, Schaffneria, and 

 Camptosorus, with the veins 

 reticulated. With the indusia 

 connate in pairs, back to back — 

 Diplazium, with free veins ; 

 CaWpteris, with connivent 

 veins ; and Oxygonium, with 

 the veins semi-reticulated. 



The Didymochlcenece com- 

 prise two genera. One of these 

 is the singular genus Didtf- 

 mochlcena, in which a peculiar 

 fructification occurs ; the sorus is short elliptic-oblong, and the vein is 

 elevated into a crest-like ridge with which the indusium is united along 

 its centre, both the sides and rounded ends being free ; this genus has 

 free veins. The other is Mesochlcena, in which the veins are connivent. 



§13. Asplenik^ : Asplenium obtusatura. 



§14. DIDYMOCHL-ENE.E : Didymochlaena lunulata. 



The remaining group (b) has naked or spuriously -indusiate sori. 

 This term, spuriously -indusiate, though easily enough defined, is not 

 quite so readily applied, in consequence of the many transition states 

 between it and what may be called true indusia. What is meant, 

 however, is that whereas the true indusium consists of a membrane 



