236 DR, A. C. SEWARD: 
first encounter Ferns which agree closely in habit as also in the characters of 
the sori with recent representatives of the family (Map D) (PI. 19). 
Specimens were referred to the Marattiaceæ by the late Prof. Zeiller from 
Triassic rocks in Madagascar. Ferns of similar type, with long strap-shaped 
pinnæ, described either as species of Marattiopsis or Daneopsis are abundant 
in Rhetie floras; they occur in Scania, India, Tonkin, South Africa, 
Australia, and elsewhere. It has recently been demonstrated by Halle that 
the sori of a Rhatie species of Danæopsis, D. fecunda, consist of contiguous 
but separate sporangia covering the under side of the lamina on each side of 
the midrib: as he states, the comparison of Dan@opsis fronds of this type 
with those of the genus Danea is entirely unwarrantable as the sporangia 
are of the Angiopteris type. ' 
Marattiaceous fronds with fertile pinnæ of linear form are common in 
Jurassic beds: they are recorded from England, Scania, Bornholm, Poland, 
India, China ; and a fern of different habit, but with sori suggesting com- 
parison with those of some recent Marattiaceæ, has been described from 
Jurassic rocks in Afghanistan; A few ferns from Jurassic and Cretaceous 
strata in North America have been recorded under the names Daneopsis and 
Angiopteridium, but especially in the case of the latter genus the specimens 
are sterile and afford no definite evidence of affinity to the Marattiaceæ. 
Fertile pinnæ from the Jurassic plant-beds of Oregon described as a species 
of Danæopsis, characterised by linear sori of separate sporangia but without 
any indication of actual structure, may belong to the Osmundaceæ : the pinnæ 
agree closely with those of the well-known form Cladophlebis denticulata, 
some examples of which are certainly Osmundaceous. 
There are a few records of Marattiaceous ferns from Cretaceous and 
Tertiary floras, but the maximum development of the family as we now 
know it seems to have been in pre-Cretaceous times. 
Conciusion. In conclusion I have to confess that the very incomplete 
retrospect based on a selection from the fragmentary documents in the 
earth’s crust leads to no very definite conclusion. Darwin in a letter to 
Hooker in 1869 wrote “ At each epoch the world tends to get peopled 
pretty uniformly, which is a blessing for Geology.” The comparative 
uniformity of the world’s vegetation in its general composition at certain 
stages in the history of the earth is a fact helpful to the historical geologist 
in arranging his chapters. It has, however, a significance from the point of 
view of evolution which may be fundamental. * In these books of stone we 
find the soul of history”; but the problem is to recognise the soul when 
we find it. Over vast areas whole communities seem to have appeared and 
disappeared simultaneously. Beneath this exaggerated statement there isan 
underlying truth. As Suess says, “It is the organic remains, no doubt, 
which afford us our first and most important aid in the elucidation of the 
