CHAPTER XVIII 



COENOPTERIDACEAE 



The plants included under this heading are all fossils, and include the 

 Botryopterideae, the Zygopterideae, and the Anachoropterideae: but it is 

 possible that others may be added as knowledge of the fossils increases. 

 They are all Palaeozoic types, and are distinct from any living Ferns. Still 

 there is no reason to doubt their Fern-nature, though they appear as general- 

 ised rather than specialised types. Their recognition as Ferns is based upon 

 the external characters of the shoot with pronounced megaphyllous character, 

 while the usual circinate vernation of the large alternate leaves has been 

 seen in some of them. But more particularly it rests upon the anatomical 

 details of axis and leaf, and upon the fact that in some of them sporangia 

 containing numerous homosporous spores have been found, borne upon the 

 distal region of their relatively large branched sporophylls. Finally, Scott 

 has shown in Staitropteris oldhainia that the spores possessed the capacity 

 for germination within the sporangium, a feature seen in some modern 

 Ferns {Todea) {New PJiyt. v, 1906). As the three orders are somewhat 

 divergent in their characters it will be well to describe them separately. 



A. BOTRYOPTERIDEAE 



To this family the genera Gramniatoptei'is, Tubicanlis, and Botryopteris 

 are referred. They were mostly plants of relatively small size with stems 

 probably upright or straggling, which in some cases were short, bearing 

 crowded leaves {Granunatopteris, Tubicanlis, Botryopteris ramosa and hirsiita, 

 Fig. 311): in others the stem was slender with dichotomous branching, and 

 it appears to have borne leaves at distant intervals {Botryopteris cylindrical 

 Fig. 312). The leaves are imperfectly known: they have never been seen to 

 bear a well-developed lamina. They were repeatedly branched, with narrow 

 fleshy pinnules upon which the sporangia were inserted {B.forensis^. In the 

 young state the circinate vernation has been seen. Stiff conical hairs are 

 found upon the leaves having peculiar structure {B. forensis, Vol. I, 

 Fig. 187). In some instances the plants bore numerous adventitious 

 roots with diarch structure {Tnbicaiilis, B. ramosa, Fig. 311). Though the 

 habit of these plants is still imperfectly known, their Fern-nature seems 

 clearly established, while their anatomy, which is better understood, con- 

 firms that conclusion. 



The vascular system of the stem is protostelic, giving off monodesmic 

 leaf-traces to the several leaves. The roots which are often numerous also 



