Professor A. C. Seward — Floras of the Past. 561 



One of the most striking facts afforded by a study of the Mesozoic 

 fern vegetation is the former extension and vigorous development of 

 two families, tlie Dipteridinge and Matoninese, which are now 

 confined to a few tropical regions and represented by six species. 

 The fertile fragment of a frond of Matonidium exposed by a_stroke 

 of the hammer in a piece of iron-stained limestone picked up on the 

 beach at Haiburn Wyke (a few miles north of Scarborough), is 

 hardly distinguishable from a pinna of the Malayan Matonia 

 pectinata. Eh^tic and Jurassic ferns referred to the genus 

 Laccopteris afford other examples of the abundance of the Matonineee 

 in the northern hemisphere during the earlier part of the Mesozoic era. 

 The modern genus Dipteris, with its four species occurring in 

 India, the Malayan region, Formosa, Fiji, and New Caledonia, stands 

 apart from the great majority of Polypodiaceous ferns, and is now 

 placed in a separate family — the Dipteridinge. Like Matonia it is 

 essentially an ancient and moribund type with hosts of ancestors 

 included in such Ehaetic and Jurassic genera as Dictyophyllum, 

 Camptopteris, and others which must have been among the most 

 conspicuous and vigorous members of the Mesozoic vegetation. 



E. Floioering Plants. — Our retrospect of the march of plant-life 

 has so far extended to the dawn of the Cretaceous period, a chapter 

 in geological history written in the rocks that constitute the 

 Wealden series of Britain exposed in the Sussex cliffs and in the 

 Weald district of south-east England. According to the geologist's 

 reckoning, the Cretaceous period is of comparatively modern date ; 

 it occupies a position near the summit of a long succession of ages 

 representing an amount of time beyond the power of imagination 

 to conceive. 



One interesting fact as regards the composition of the Jurassic 

 flora is the absence of any plants that can reasonably be identified 

 as Angiosperms. In the Wealden flora of England no vestige of an 

 Angiosperm has been found ; this statement holds good also as 

 regards Wealden floras in most other regions of the world. On the 

 other hand, as soon as we ascend to strata of slightly more recent age 

 we are confronted with a new element in the vegetation, which with 

 amazing rapidity assumes the leading role. It is impossible to say 

 with confidence at what precise period of geological history the 

 Angiosperms appeared. When the rocks that now form the 

 undulating country of the Weald were being accumulated as 

 river-borne sediments on the floor of an estuary, this crowning act 

 in the drama of plant evolution was probably being enacted. 



I have already pointed out that we have as yet recognised no 

 Angiosperms in the Wealden floras of England, Spitzbergen, 

 Germany, France, Austria, Belgium, Eussia, and Japan ; but from 

 plant-bearing rocks of Portugal, regarded as homotaxial with those 

 which British geologists speak of as Wealden, the late Marquis 

 of Saporta named a fragment of a leaf Alismacites primcevus, 

 a determination that, while possibly correct, cannot be accepted as 

 conclusive testimony. In Virginia and Maryland there occurs a thick 

 series of strata known as the Potomac formation, from which a rich 



DECADE IV. VOL. X. — NO. XII, 36 



