INTRODUCTION TO CRYPTOGAMIC BOTANY. 539 



pave the way to Lindscea and its allies, which have linear mar- 

 ginal sori, for the most part continuous, but sometimes regu- 

 larly interrupted. The indusium opens towards the margin 

 of the frond, and not away from it, as in Pteris, a consequence 

 of its not being merely the altered margin. The sori, more- 

 over, connect the tips of the veins and veinlets. In Lindscea 

 we have frequently trapeziiform or cuneate pinnce, resembling 

 somewhat those of Adiantum. Schizolortia has the sori 

 parallel with the margin, as in Lindscea, but the venulation is 

 angularly anastomosing, instead of flabellate. Isohina has a 

 marginal bilabiate indusium, and differs from Lindscea in 

 having deciduous pinnce. Dictyoxij^hiuvi has simple lineari- 

 lanceolate fertile fronds, inframarginal sori, and compound 

 anastomosing veinlets, with variously directed free veinlets in 

 the areolse. Synopldebium differs from ScJtizoloma in the 

 eccentric midrib. This, again, is mostly a tropical or subtro- 

 pical division. Davcdlia canariensis is a well-known object 

 of cultivation in our conservatories. One species extends to 

 New Zealand, and two of Lindscea. 



13. AsPLENiACE^, Presl. 



Sori globose, linear-oblong or more frequently linear, seated 

 on the back, rarely at the tip of a vein or veinlet ; indusium 

 lateral, persistent, free on the side which is opposite to the 

 margin of insertion ; rhizoma subglobose, rarely creeping, 

 more rarely still forming a low unarmed caudex. 



612. This tribe is at once distinguished from Aspidiacece 

 and Davalliacece by the lateral persistent indusium, which is 

 free opposite to the margin of insertion. This freedom, more- 

 over, does not take place by the mere dehiscence of the 

 indusium, but is essential to the structure. The tribe is 

 divisible into five sections, allied respectively to Scolopen- 

 drium, Diplazia, Aspleyiium, Blechnum, and Cystopteris. 



613. The first is distinguished by the sori being approxi- 

 mated and parallel on the proximate sides of two contiguous 

 parallel veinlets, the free margin of both being in consequence 

 opposite. The sori in Scolopendrium look like one, but are 

 really double, each with its own indusium. The indusium is 

 not, in fact, a single indusium fixed on either side and bursting 



