34 COENOPTERIDACEAE [CH. 



C. ANACHOROPTERIDEAE 



The sori of a somewhat isolated type, Anachoropteris , from the Bohemian 

 Middle Coal Measures, add a further step of structure (see Scott, Fossil 

 Botany, 3rd. ed., Part i, p. 354). The stem is unknown. The leaves are 

 characterised by a wide, strongly reflexed petiolar strand, having its convex 

 curve adaxial, as in Ttcbicmdis (Fig. 153, C, Vol. l). The sori were borne on 

 the incurved margins of small pinnules. Each consisted of four sporangia 

 invested by a thick outer wall common to them all, so as to form a synan- 

 gium. The sorus was borne on a receptacle having vascular supply. The 

 whole structure suggests a small and simple, but marginal synangium of 

 the type of Marattia. 



The genus Anachoropteris Corda is held by Scott ij.c. p. 352) as the type 

 of a family separate from the Zygopterideae and Botryopterideae. To this 

 a provisional assent may readily be given. 



Naturally nothing is known of the gametophyte of the Coenopteridaceae 

 beyond the fact that the spores did germinate in Stauropteris, with the first 

 results not unlike those seen in some modern Ferns. 



Comparison 



The Coenopteridaceae, comprising the three families now described, have 

 features in common which justify their being grouped together under a 

 ■comprehensive head, though as Scott remarks {Studies, p. 357), "we are at 

 present without any clear indication of their supposed common ancestry." 

 They were all plants of moderate size, some quite small {Botryopteris). Their 

 shoot was frequently upright, and this was certainly so with the ancient 

 Devonian Asteropteris: but others had clearly a prone habit sometimes 

 with a greatly extended rhizome, as in Metaclepsydropsis. The similarity in 

 structure of axis and leaf has been shown in Botryopteris cylindrica to be 

 consistent with a theory of origin of leaf and axis from an indifferent 

 dichotomous branch-system (p. 16). The form of the leaves is rarely well 

 known, but the anatomy of the rachis indicates in some of them a form 

 comparable with that of living Ferns: and even the circinate vernation of 

 the young leaves has occasionally been preserved. Simple or curiously sep- 

 tate hairs are present, but no flattened scales, a fact which accords with the 

 primitive position assigned to the family. Their anatomy is clearly based 

 upon a primitive type such as that seen in Botryopteris. The stem is in all 

 cases protostelic: but it is liable to elaborations which will presently be 

 shown to be related to their actual size. Those elaborations consist on the 

 one hand in differentiation of the xylem, on the other of modifications of its 

 outline,, and also of that of the stele itself Their petioles were always 



