XXIX] DICKSONIEAE 263 



phyllaceae, the lateral dehiscence is thus effective as in other Gradatae. But 

 the succession of the sporangia is not long continued. 



As regards its sorus and sporangium TJiyrsopteris appears to be one of 

 the least specialised of Leptosporangiate Ferns, and to show analogies 

 with Loxsomopsis and with Hymenophylliuii. The distal curve of the annulus 

 runs almost in a horizontal plane, and thus is reminiscent oi Anemia, while 

 the low organisation of the stomium also indicates a primitive state. On 

 the other hand there are distinct analogies with Dicksonia, with which its 

 dendroid habit and dermal hairs relate it. There appears little reason to link 

 TJiyrsopteris with the Cyatheae, from which the absence of scales, and the 

 strictly marginal sorus definitely remove it. It finds its best place as the 

 sole survivor of a separate and archaic family, related to the Dicksonieae, 

 and it is probably akin to Cojiiopteris, a Fern of the Jurassic Period. 



Prothalli of TJiyrsopteris have been raised by Boodle at Kew, and by 

 Miss Stokey at Holyoke College, Mass. The latter has not found them to 

 bear either hairs or scales : but naturally rhizoids are present. A detailed 

 description will be published shortly. 



//. DicJcsonieae 



This sub-family is here treated in the same limited sense as in the Origin 

 of a Land Flora, p. 592: that is to say, excluding \Patania (see Synopsis 

 Filicum, p. 52), but retaining Balantiuni Kaulfuss, DicJisojiia L'Heritier, 

 and Cibotiwn Kaulfuss, as they are recognised by Diels {Natiirl. Pflanzenfam. 

 I, 4, p. 1 19). The Ferns thus grouped vary in habit from low creeping stocks 

 to lofty tree-ferns. Their leaves are repeatedly pinnate, and bear numerous 

 marginal sori, but without any clear differentiation of sterile from fertile pinnae. 

 The sori are protected by a two-lipped indusium, but the lips are more or 

 less unequal, and their characters have been used in generic distinction. The 

 receptacle is itself marginal, the lips of the indusium originating as outgrowths 

 of the upper and lower surfaces of the pinnule as in TJiyrsopteris, the 

 Hymenophyllaceae, and ultimately the Schizaeaceae also (Fig. 530). There 

 is thus a strict local correspondence between the sori of all of these Ferns. 

 The differences are mainly in habit and size. All of them are alike in having 

 hairs as their dermal covering, while scales (ramenta) are consistently absent. 



Creeping stems such as those of Cibotittm Baroniet.z, and Balantiuni 

 Culcita are massive, and if cut transversely at an internode show a very 

 large solenostele surrounding a distended pith (Fig. 531). From this an 

 undivided meristele passes off to each leaf. The leaf-gaps may overlap, so 

 that more than one may be traversed, and the structure may be technically 

 dictyostelic. The leaf-trace is a broad ribbon with infolded margins, and 

 very shortly after its departure from the stele it breaks up into a number of 

 isolated strands arranged horse-shoe fashion, as seen in transverse section 



