172 SCHIZAEACEAE [CH. 



also the more complex antheridial wall, and Miss Twiss states that there 

 is a large number of the sperms in each antheridium (156): while 32 sper- 

 matocytes may be traversed in a single vertical section. These features 

 appear as evidence of a primitive relation. Anemia and Mohria with a 

 smaller spore-output have also the simpler structure of the antheridial wall, 

 while in all the other three genera the spermatocytes appear less numerous 

 than in Lygodiuvi (Fig. 457, C). 



There appears to be nothing calling for special remark in the embryology. 



Comparison 



There is no Family of Ferns more interesting comparatively than the 

 Schizaeaceae. Their importance is due partly to the intermediate place 

 which they take as a consequence of comparison with others, partly to 

 their early fossil history, but chiefly to the wide range of the anatomical 

 and other features of the living types. This gives to them, more than to 

 any others, a synthetic character. At the same time their main features, 

 and especially their sporangia, define them as constituting a naturally 

 circumscribed Family. 



In their external form they present both the upright radial, and the 

 creeping dorsiventral habit, with distal dichotomy of the axis. In their 

 leaf-architecture they show a wider latitude than any other Family: they 

 pass from equal dichotomy, through all grades of sympodial to extreme 

 dichopodial development, finding their climax in the prehensile leaves of 

 Lygodinin which may extend to 100 feet in length. But even their most 

 specialised and advanced foliar types are still referable to modifications of 

 dichotomy. From the point of view of anatomy these Ferns comprise the 

 permanent protostele of Lygodmm: the medullated and otherwise modified 

 protostele of ScJiizaea, the solenostele of Anemiorrhisa, the dictyostele of 

 Mohria, and even the basket-type of dictyostele of Anemia Phyllitidis. 

 Thus all the leading grades of modification of stelar structure are exemplified 

 within the Family. The undivided leaf-trace, based upon the C-shaped 

 trace of the Osmundaceae, is always retained ; but it is sometimes 

 greatly modified as in Lygodiuvi. The venation of the blade, though 

 open as a rule, is sometimes coarsely reticulate {Lygoditim, Anemia), 

 while the fertile segrnents show in their various forms obvious evidence of 

 protection against drought. The dermal appendages are as a rule simple 

 hairs, as is usual in primitive Ferns, but Alohria, in many respects an 

 advanced type of the P"amily, bears flattened scales, thereby confirming its 

 relatively advanced position. At the same time it shows how this apparently 

 minor feature follows other more important structural characters, and sup- 

 ports conclusions derived from them. The whole Family is held naturally 

 together by the position and structure of the sporangia. Though the form 



