566 



NATURE 



[October 8, 1903 



spread section in the Jurassic period ; we find them in 

 Jurassic rocks of Victoria, as well as in several regions in 

 Europe, North America, and the Arctic regions. 



The fertile fronds of many of the fossil Cyatheaceae bear 

 a striking resemblance to that isolated survivor of the 

 family in Juan Fernandez — Thyrsopteris elegans. It is true 

 that a considerable number of ferns of Jurassic and Wealden 

 age have been described by the generic name Thyrsopteris 

 without any adequate reason ; but, neglecting all doubtful 

 forms, there remain several types represented in the Jurassic 

 flora of Siberia, England, and other parts of the world, 

 which enable us to refer them with confidence to the 

 Cyatheaceae and to compare them more particularly with 

 the sole existing species of Thyrsopteris. The Gleicheni- 

 aceae, at present characteristic of tropical and southern 

 countries, were undoubtedly abundant in the northern hemi- 

 sphere in early Cretaceous days ; abundant traces of this 

 family are recorded from Greenland as well as from more 

 southern European latitudes. 



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, the DipteridinJE and 

 Matonineae, which are now confined to a few tropical 

 regions and represented by six species. The tall graceful 

 fronds of Matonia pectinata, forming miniature forests on 

 the slopes of Mount Ophir and other districts in the Malay 

 Peninsula in association with Dipteris conjugata and 

 Dipteris Lobbiana, represent a phase of Mesozoic life which 

 survives — 



" Like a dim picture of the drowned past." 



The fertile fragment of a frond of Matonidium exposed 

 by a stroke of the hammer in a piece of iron-stained lime- 

 stone 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. Rhaetic and 

 Jurassic ferns referred to the genus Laccopteris afford other 

 examples of the abundance of the Matonineae in the northern 

 hemisphere during the earlier part of the Mesozoic era. 



The modern genus Dipteris, with its four species occur- 

 ring in India, the Malayan region, Formosa, Fiji, and New 

 Caledonia, stands apart from the great majority of Poly- 

 podiaceous ferns, and is now placed in a separate family — 

 the Dipteridinae. Like Matonia it is essentially an ancient 

 and moribund type with hosts of ancestors included in such 

 Rhsetic and Jurassic genera as Dictyophyllum, Campto- 

 pteris, and others which must have been among the most 

 conspicuous and vigorous members of the Mesozoic vegeta- 

 tion. The appended table illustrates in a concise form the 

 former extension of the Matonineas and Dipteridinae : — 



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 com- 

 paratively 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. On 

 the other hand, to quote from Huxley's lecture on a piece 

 of chalk, " not one of the present great physical features 

 of the globe was in existence. . . .Our great mountain- 

 ranges, Pyrenees, Alps, Himalayas, Andes, have all been 

 upheaved since the chalk was deposited, and the Cretaceous 

 sea flowed over the sites of Sinai and Ararat." This Cre- 

 taceous epoch, so recent geologically if measured by the 

 standard of the antiquity of the everlasting hills, has a 

 remoteness beyond our power to appreciate. 



One interesting fact as regards the composition of the 

 Jurassic Flora is the absence of any plants that can reason 

 ably 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 rSle. 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. 



" Nothing," wrote Darwin to Sir Joseph Hooker in 1881, 

 " is more extraordinary in the history of the vegetable 

 kingdom, as it seems to me, than the apparently very 

 sudden or abrupt development of the higher plants. I 

 have sometimes speculated whether there did not exist some- 

 where during long ages an extremely isolated continent, 

 pel haps near the South Pole." We date the appearance of 

 a new product of evolution from the age of the strata in 

 which it first occurs ; but this may well be a misleading 

 criterion : all that we can say is that at a particular period 

 certain new types of organisms are brought within our ken. 



To quote Darwin again : " We continually forget how- 

 large the world is, compared with the area over which our 

 geological formations have been carefully examined ; we 

 forget that groups of species may somewhere have long 

 existed, and have slowly multiplied, before they invaded the 

 ancient archipelagoes of Europe and the United States. 

 We do not make due allowance for the intervals of time 



Geographical Distribution of the Matonineae and Dipteridinae. 



Could we but question these survivors from the past, we 

 should hear a tragic story of hopeless struggle against 

 stronger competitors, and learn the history of their gradual 

 migration from an ancient northern home to regions at 

 th3 other end of the world. 



e. Flowering Plants. 

 Our retrospect of the march of plant-life has so far ex- 

 tended to the dawn of the Cretaceous period, a chapter in 



NO. 1 77 1, VOL. 68] 



which have elapsed between our consecutive formations, 

 longer, perhaps, in many cases than the time required for 

 the accumulation of each formation." 



On another occasion Darwin wrote to his friend Hooker : 

 " The rapid development, as far as we can judge, of aH 

 the higher plants within recent geological times is an 

 abominable mystery." Such evidence as we possess, meagre 

 as it admittedly is, shows that " this overshadowing type 

 of plant-life " no sooner appeared than it asserted itself 



