996 DR. A. C. SEWARD : 
Measures, bearing circular sori with a few sporangia which were probably 
annulate, is often quotéd as a probable Paleozoic representative of the 
Gleicheniaceæ ; but the evidence is not conclusive. We can at least state 
with confidence that fronds of certain Paleozoic Pteridosperms show a 
scheme of branching apparently identical with that of recent Gleicheniacex. 
In itself this is of no great value in view of the fact that dichotomous 
branching is probably a primitive feature of plant architecture. 
Fossil species of the family Gleicheniacex are fairly widely spread in the 
Northern Hemisphere far beyond the present limits of Gleichenia. In early 
Cretaceous times Ferns hardly distinguishable from existing species belonging 
both to the Zugleichenia and to the Dicranopteris sections were particularly 
abundant in Western Greenland far within the Arctic circle, and specimens 
from Upper Jurassic or possibly Wealden beds in Spitzbergen have also been 
referred to Gleichenites. 
The oldest examples which can be assigned with confidence to the family 
are from Keuper strata in Switzerland, and a portion of a frond of the 
Eugleichenia type, but with no fertile segments, is recorded from beds of 
the same age in France. From beds in New Zealand, which may be Rheetic 
in age, Arber has described specimens as species of Microphyllopteris, a name 
instituted by him as being more appropriate than Gleichenites in the absence 
of proof of affinity to the Gleicheniacew. To Arber’s genus Walkom refers 
specimens from the Rhætie of Queensland. Portions of sterile fronds from 
the Rhietie flora of Franconia bear a striking resemblance to some of the 
recent species of the Eugleichenia type.  Gleichenites was unquestionably a 
member of the Lower Jurassic flora of Poland: it is represented by well- 
preserved fronds, though without fertile pinn:e, in Jurassic rocks in India. 
Examples are recorded from Upper Jurassic rocks in Sutherland on the 
North-East coast of Scotland, and from the same beds a f agment of a 
rhizome was discovered with a protostele of the Gleichenia type. From 
Upper Jurassic, or possibly Wealden, strata in Patagonia (leichenites has 
been described by Halle. It is, however, in the Cretaceous floras that the 
genus was especially abundant: good examples are known from several 
European localities; in West Greenland Gleichenites flourished most 
abundantly. It was also well represented in the Wealden flora of Belgium 
in which Dr. Bommer tells me he has discovered rhizomes with steles 
agreeing with those of recent species. Similarly the genus occurs in Lower 
Cretaceous strata in England, Germany, France, and other European 
districts including the Balkans ; it is also represented in the Cretaceous flora 
of Sakhalin Island. Comparatively few satisfactory specimens have been 
found in North America: the best are those on which Knowlton founded the 
species Gleichenites pulchella, showing dichotomously branched fronds with 
pinne thickly set with very small segments, from the Upper Cretaceous of 
Wyoming. During Tertiary times (rleichenites seems to have lingered in 
Europe ; but the records are few and fragmentary. 
