The Present Position of Palaeozoic Botany. 



179 



described by Renault. The stem (probably a rhizome) has a remarkably 

 simple structure, the stele consisting- of a solid strand of tracheides 

 surrounded by phloem (Fig. 12). The relatively large petioles, borne 

 in a spiral order on the stem, contain a single bundle, with a charac- 

 teristic w-like transverse section, the structure being somewhat more 

 complex in B. forensis than in the smaller forms B. hirsuta and 

 B. ramosa. In the case of the French specimens there is evidence 

 as to the form of the compound leaves and their circinate vernation. 

 The stem also bore numerous diarch adventitious roots, an indication 

 of its rhizome-nature. 



Fig-. 12. Botryopteris hirsuta. Transverse section of stem, giving- off a petiole and 

 roots. X.S., xylem of stem; x.p., xylem of petiole; r^, r-, adventitioiis roots; h, hairs. 



X 15. 



In all respects the characters of the vegetative organs were 

 those of a simple type of Fern, comparable, as Renault at once re- 

 cognized, to the recent Hymenophyllaceae. The fructifications, dis- 

 covered by the same observer in B. forensis, confirmed the Filicinean 

 affinities of the genus, but at the same time showed it to be very 

 different from any Fern now living. The sporangia, densely grouped 

 in tufts on the naked rachis of a modified frond, are of large size 

 (1.5— 2 mm in length) and are characterized by the broad annulus, 

 forming a longitudinal band many cells in width, running the whole 

 length of the sporangium on one side. No very close analogy for 

 this structure is to be found among recent Ferns, though the areola 



12* 



