392 ANNUAL REPOET SMITHSONIAN INSTITUTION, 1918. 



cites, or Lepidophytic as in Naiadita, or Arthrophytic as in Con- 

 vallarites. 



Considering the march of vegetation during the Triassic as a 

 whole it may be noted that succeeding the sparsely represented floras 

 of the earlier Triassic, there appeared throughout the world during 

 the Upper Triassic extensive floras which, while containing surviving 

 stragglers from the Paleozoic, decidedly foreshadowed the cosmo- 

 politan floras of the succeeding Jurassic time. Regarding the place 

 of origin of these Triassic floras, it may be said that they contain a 

 mixture of survivors from the northern cosmopolitan and the Gond- 

 wana Land Permian floras. The undue emphasis that has often 

 been placed upon Glossopteris and the habit of speaking of Schi- 

 zoneura and Phyllotheca as members of the Glossopteris flora has 

 led some students to consider that the Triassic flora was evolved in 

 Gondwana Land. A careful analysis of the Triassic floras, how- 

 ever, for which space is lacking in the present article, clearly shows 

 that this was not the case, but that the more prominent elements in 

 the Triassic floras had northern ancestors, as, for example, Voltzia, 

 Pterophyllum, Baiera, Ginkgo, Sphenozamites, Phyllotheca, Neoca- 

 lamites, etc., and originated in the northern land masses. 



THE JURASSIC FLORAS. 



The Jurassic was a time of warm climates, shallow seas on the 

 margin of the continents, and low-lying lands. Its deposits are not 

 sharply separated from the underlying Triassic or the overlying 

 Lower Cretaceous, consequently, the contrast in the succession of 

 floras are, in the main, the evolution of new specific types rather than 

 of greater groups. Paleontologically the Jurassic is characterized 

 primarily by the swarming marine faunas of its shallow seas. Fol- 

 lowing the almost world-wide occurrence of the rich palustrine Kha- 

 etic floras of late Triassic age, the record consists of a succession of 

 sandy, clayey, and calcareous rocks of marine origin, relatively poor 

 in their representation of the contemporaneous terrestrial vegetation, 

 although most of the Jurassic stages are fairly well represented by 

 fossil plants in some part of the world. 



Calcareous algae of both marine and fresh waters (charophytes) 

 are not uncommon, but not especially noteworthy. Several modern 

 appearing Hepatics have been recorded. Ferns, Cycadophytes and 

 Conifera comprise the bulk of the vegetation. Many of these are 

 generic types which ranged from the Triassic to the Lower Creta- 

 ceous. The magnificent lyre ferns (Dipteriaceae) of the Triassic sur- 

 vived in some of their manifestations in Jurassic times, as did some 

 of the Triassic Marattiaceae. The former were not, however, so 

 characteristic of Jurassic times as were the representatives (Laccop- 



