i88 BLECHNOID FERNS [ch. 



Other details are liable to appear that may be important for comparison: 

 for instance secondary branch-veins are frequent, lying in the space between 

 the forks of the primary veins, and supernumerary sori may be attached to 

 them as at (x), Fig. 706, 28, c, d. These sori are probably new formations in 

 the sense that they are not directly derivative by disintegration from the 

 coenosorus. Such innovations may be found established as regular features 

 in Pkyllitis, and they occur frequently in Ferns with sporophylls of widely 

 continuous expanse. 



The development of the coenosorus of the variety Krebsii has been found 

 to correspond to that oi B. spicant \sfheve a normal pinna is cut (Fig. 706, 29,^'): 

 but if sections be cut so as to traverse both sides of a narrow loop of the 

 coenosorus, such as occurs on a widened fertile pinna, the appearance when 

 young is as in Fig. 706, 29, /, and when older as in g, where the opposed 

 indusial flaps overlap one another. The structure in fact corresponds very 

 closely to that in Pkyllitis (Fig. 669, 31, a, b). The general conclusion which 

 follows is that B. puncttdatum var. Krebsii xs^ a Blechnoid Fern which has 

 widened its fertile pinna beyond that normal {ox\Lomaria: and that this 

 widening has been accompanied by a sinuous curving of the coenosorus, 

 and often also by its disruption, while sometimes extra branchings of the 

 veins appear, together with a formation of supernumerary sori. The final 

 result is a structure closely comparable to that seen in Pkyllitis Scolo- 

 pendrium. 



Phyllitis Ludwig (= SCOLOPENDRIUM Adanson) 

 The fact that Kunze first described the Natal variety of B. pwictulatuin 

 under the name of Scolopendj-iuin Kuitzii, while subsequent observations 

 accentuate its similarity to the Hart's Tongue Ferns, raises the question of 

 their relation to other Ferns, in particular to Blecknum on the one hand and 

 to Aspleniuui on the other. They have usually been ranked with the latter. 

 In the most extended sense the genus Pkyllitis Ludwig includes four sec- 

 tions, differing rather in habit than in their soral characters. Their leaves are 

 all of a highly condensed type, and they may therefore be held as derivative 

 from Ferns with more elaborate leaf-form. The genus comprises less than a 

 dozen species, of which the best known is the common Hart's Tongue, 

 Pkyllitis Scolopendj'ium (L.) Newm. 



The habit of the Hart's Tongue is well known : its upright stock bears 

 homophyllous leaves, almost entire and broadly winged, with the character- 

 istic sori extending far from the well-marked mid-rib towards the sinuous 

 margin. The stock contains a vascular system of the Blechnoid type. The 

 root-steles come off each from one of the meristeles just below the leaf-gap. 

 As the gap opens it gives off right and left the paired strands of the leaf-trace. 

 Passing up the leaf-stalk the pair may fuse to form the complex X-shaped 



