544 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



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superior vein ; indusium inferior, scarious, at length splitting 

 into several lobes ; receptacle generally very small. 



620. A small tribe consisting of only a few genera. Pera- 

 nema or Sphceropteris has a large globose rhizoma, and 

 pedunculate sori ; the tips of the veins are clavate and glan- 

 dular. Diacalpe differs only in its apparently sessile sori. 

 Physematium has sessile sori with a nearly entire indusium 

 and sub-globose rhizoma. Woodsia differs from Physema- 

 tium in its beautifully laciniated indusium, and contains two 

 of our rarest and most interesting Ferns. Hypoderris is 

 very close to Drynaria, and distinguishable only by its very 

 obscure but perfect cupshaped indusium, like that of Woodsia, 

 from which genus it differs in its anastomosing not simple 

 veinlets. Thyrsopteris and Cibotium are inserted here by 

 Presl, but their proper place is amongst Dicksoniacece. 



16. Hymenophyllace^, Endl. 



Indusium cupshaped or bivalvate, formed partly of the 

 frond, or arising from and threaded by the excurrent costa, 

 to the base of which are attached the sporangia mixed with 

 paraphyses. 



621. In consequence of the membranaceous reticulated fronds 

 resembling those oi Symphyogyna (Fig. 110, a, and 95, a, 6), 

 Presl and others have considered the curious and beautiful 

 plants of which this tribe is composed as constituting a totally 

 distinct order ; but they are so closely connected with Davallia 

 by means of Prosaptia and Loxsoma, and with Thyrsopteris 

 by Trichomanes pluma and others, that, as it appears to me, 

 there is little doubt about the matter ; and if the distinction 

 of oblique and vertical rings {Helicogyratce and Catheto- 

 gyratm, Presl) is to be kept up, they must be placed in the 

 same section with Gleichenia and Gyathea. The coriaceous 

 frond of Loxsoma, accompanied by the columella and oblique 

 ring of Trichomanes, as evidently removes any uncertainty 

 which might arise from the structure of the leaves.* Hyme- 



* The frond is not equally reticulate in all the species. In the section 

 Hymenostachys of Trichomanes, a section in -wliich the veinlets anasto- 

 mose, the structure approximates that of ferns with a close reticulate 

 venation. In Trichomanes reniformc a transverse section shows two 



