XXXIII] COMPARISON 309 



such from the Mesozoic, and possibly from the Palaeozoic Period. On the 

 other hand, the primitive Marginales, as represented by the living Dicksonia- 

 ceae, differ not only in the marginal position of their sori, but also in their 

 two-lipped protective indusium, in their dermal appendages being hairs and 

 never scales, and in their sporangial segmentation, so far as yet observed. 

 The dendroid habit, which led earlier systematists to confuse them with 

 the Cyatheaceae, is seen to be a polyph}'letic character, as witnessed by the 

 Osmundaceae, and Blechnoideae, etc. It cannot then be held as a valid 

 indication of relationship. The conclusion which follows from this wide 

 comparison is that the primitive Superiiciales have been phyletically distinct 

 from the primitive Marginales from very early times, and in fact before the 

 gradate state was adopted : and that their recognition as two parallel series 

 in the phyletic Classification of the Filicales is justified. In addition to habit 

 and soral features the distinction has been supported by palaeontological 

 evidence and by comparative anatomy. These factors seem to have been 

 little regarded by Prof von Goebel. But here they are held to be essential 

 in leading to a just balance of opinion upon such a question. 



A further circumstance that has confused the issue is that in many of the 

 later derivatives of the Marginales the sorus may pass adaptively to 

 a superficial position, while doubtless the converse is possible among the 

 Superficiales. The result of this is that it becomes difficult to pursue the 

 distinction into the more modern Leptosporangiates. This will be found to 

 be a formidable problem in Vol. III. But such difificulties do not justify any 

 negation of the broad conclusion which follows from a comparison of pre- 

 Leptosporangiate types in upward sequence. It is from them that the 

 phyletic lines must be traced, not from their later derivatives. 



The Cyatheaceae are so closely related to certain Ferns with mixed sorus 

 that there can be no doubt that the further transition from a gradate to a 

 mixed state has taken place here, as it certainl}- did in the Dicksoniaceae. 

 The genus Diacalpe has a mixed sorus (Davie, ^«;/. of Bot. xxvi, 19 12, p. 245). 

 It used to be included in the Cyatheaceae {Synopsis Filicum, p. 45), though 

 more recently it has been placed in the Woodsieae. Peranema, too, which 

 also has a mixed sorus (Davie, /.t-.), is included in the Woodsieae, a group 

 which will be held over for detailed treatment later. The genus Woodsia 

 itself is clearly related to the gradate Cyatheaceae, but the group bridges 

 over the transition to the mixed state not only b\- the genera named, but 

 also by the shade-type Hypoderris. A read}- transition is thus suggested 

 to that large body of Leptosporangiate Ferns that will be st\4ed the 

 Dryopteroideae. On the other hand through Matteiiccia, which is a gradate 

 genus, a distinct line, characterised by soral fusions as well as b\- a mixed 

 sorus, leads to the large sequence that may be grouped under the heading 

 of the Blechnoideae. All of these may be held as related by descent to the 



