6 INTRODUCTION TO VOLUME II 



The positive facts of Palaeontology relating especially to the Ferns have 

 been summarised critically by Seward {Fossil Plants, ii). They indicate 

 the following sequence of appearance for those Classes of Ferns which a 

 general comparison has indicated as being relatively primitive. The first 

 Ferns of which any record exists were the Coenopteridaceae\ including the 

 Botryopterideae, and Zygopterideae, with which the Anachoropterideae 

 may also be associated. They are known as fossils only, and are represented 

 from the Culm and Lower Carboniferous, extending onwards to the Permian 

 (Seward, p. 432). They appear then to have died out, and to have left no 

 direct representatives. Perhaps we are right in looking upon the Ophioglos- 

 saceae as the most nearly related of living Filicales to them (Seward, p. 427). 



The Marattiaceae, as represented by the Psaronieae, have been recognised 

 from the Upper Carboniferous and Lower Permian, while Ptychocarpus iinitus 

 with its Marattiaceous sorus (Fig. 407, p. 115) occurs in the Middle Coal 

 Measures of France (Seward, p. 412). Some other Carboniferous fossils may 

 well have been really of Marattiaceous affinity, but this family appears to 

 have attained its maximum development in Mesozoic times. Its modern 

 representatives are the living Marattiaceae. 



Next in the palaeontological succession come the Osmundaceae, the re- 

 liable record of which opens with the Upper Permian of Russia. The type has 

 persisted through the Mesozoic Age, and it is represented by the Osmun- 

 daceae of the present day (Seward, p. 325). Numerous sporangia exist in 

 Carboniferous Rocks which in section are almost indistinguishable from 

 sections of the sporangia of living Osmundaceae (Bower, Ann. of Bot. Vol. v, 

 1 89 1, p. 109). It has been pointed out, however, that favourable sections of 

 a sporangium of Botryoptcris might yield a similar appearance. On the other 

 hand, Kidston has summed up his own wide experience of Fern sporangia, 

 as seen from without, thus: "In the great majority of cases where Carboni- 

 ferous plants have borne annulate sporangia, these have most frequently 

 been described as formed of a single row of cells: but in some cases at 

 least the annulus is composed of two rows of cells'^." This is seen in his 

 genus Boweria (Fig. 310). The fact seems to be that in Carboniferous times 

 the annulus as an opening mechanism was in its experimental stage: and 

 the Botryopterid or the early Osmundaceous types of sporangium gave 

 a favourable field for experiment. 



The Ferns above mentioned were undoubtedly of Palaeozoic origin. In 

 the Mesozoic Period a great evolutionary outburst of Ferns took place. 

 Several of the families which were well represented then have been traced, 

 though with doubtful credentials, to the Palaeozoic Period. This remark 



^ I prefer this title introduced by Seward, as expressing a generalised Filical type, to that of 

 " Primofilices " suggested by Arber, which appears to convey more than is desirable. But I have 

 ventured to change the form from Coenopterideae to the more comprehensive title Coenopteridaceae. 



- Fossil Plants of the Carboniferous Rocks, Vol. ii, Part iv, 1923, p. 278 



