i86 BLECHNOID FERNS [ch. xliv 



Swartz. Illustrations of the pinnae of the Natal Fern appear in Vol. I, 

 Figs. 228, 229. In all its general features, including the vascular anatomy 

 (Fig. 703), the Natal variety is typically Blechnoid. Its peculiarity lies in 

 the variability in width of the fertile pinnae, and with this goes a variability 

 of the soral characters, ranging from narrow pinnae with typical Lomarioid 

 coenosori, to broad pinnae with soral characters which resemble Scolo- 

 pendrium. Hooker {Species Filicum, III, p. 30) has described his own hand- 

 lens observations on these, in a passage that finds its natural illustration 

 in the drawings shown in Fig. 706. The authors quoted above were all 

 pre-Darwinian writers, to whom the varietal similarity of a Lomarioid Fern 

 to Scolopendriiim would appear as a striking phenomenon, rather than as an 

 evolutionary sign. It seems strange, however, that with the facts already 

 demonstrated nearly a century ago, no nearer approach should now be 

 shown in systematic works between Blechmim and Phyllitis than at that 

 early date. The former genus is still ranked with the Blechninae, and the 

 latter with the Aspleniinae. 



The slightest deviations from the normal fusion-sorus seen in B. piinctu- 

 latiun van Krebsii appear upon pinnae of greater than the normal width: 

 they consist in an outward arching of it between the veins connecting the 

 commissure with the mid-rib (Fig. 706, 28, a). Sometimes the curvature is very 

 slight: but where it is pronounced it is commonly associated with a partition 

 of the coenosorus into short lengths and very irregular (Fig. 706, 28, U). The 

 usual point of interruption is towards the anadromic end of the arch. Several 

 intermediate states are seen in Fig. 706, 28, c: in one of them the vascular 

 commissure is still complete, but the indusial flap is interrupted: in another 

 the flap is still continuous, but the commissure is interrupted, with an isolated 

 tracheide lying in the gap: in a third both flap and commissure are inter- 

 rupted (28, e\ In such cases, while the vein-endings run out towards the 

 margin, a process of the storage-xylem of the commissure underlies the 

 detached ends. More advanced states of disruption appear in Fig. 706, 28, c, d, 

 and here the detached portions of the coenosorus extend out towards the 

 margin of the widened pinna. Consequently, in extreme cases they appear 

 in pairs, with the indusial flaps facing one another, but still without any vein 

 between them, as in Phyllitis (Fig. 706, 30). 



Fig. 706. Fig. 28. Bkchnum ptnutulatuiii Sw. var. Krebsii Kunze. Portions of pinnae showing 

 various states of disintegration of the coenosorus. a = a condition very near to that normal for Blechmim, 

 especially near the apex, hut below the coenosorus is strongly arched outwards. (^ = a rather more 

 advanced state of disintegration, c, d^ still more advanced arching and disintegration, so as to resemble 

 Phyllitis: at ( x ) in these drawings supernumerary sori are present (a-aTx 2). ^=; outward arching 

 and disruption shown in greater detail, {x 10.) 



Fig* ^9- /"''^ = sections of young fertile pinna for comparison with the normal type of Blechnwn 

 (10-12, Fig. 692) and with Phyllitis (Fig. 669, 31). (x 125.) 



Fig. 30. Phyllitis Scolopeiidriiun (L.) Newrn., portion of the lateral flap of a leaf, with mid-rib, 

 showing the venation and sori: slightly enlarged. 



