THE MAIDENHAIR TREE SEWARD 455 



small scale with the short shoots of the maidenhair tree on which a 

 cluster of stalked leaves is borne at the apex. There is, however, this 

 difference: in Ginkgo the short branch persists from year to year 

 and bears fresh leaves each season: in Phoenicopsis the dwarf foliage- 

 shoot was probably shed every autumn or after a year or two ; at all 

 events, it bore only one set of leaves. Comparison may also be 

 made with the dwarf shoots of pines with two, three, or five needles; 

 the chief difference is that the leaves of Phoenicopsis are broader and 

 flat, and the structure of the epidermal layer is of another type. 

 It has been customary to assign to this genus fossil leaves having a 

 certain form and venation and borne in clusters, even though the 

 material does not furnish any information on microscopical charac- 

 ters. Dr. Florin, of Stockholm, has recently described a number of 

 leaves from Lower Cretaceous rocks associated with the basaltic 

 lavas of the now treeless Franz Josef Land (lat. 80° N.) which, owing 

 to their exceptional preservation, it was possible to examine in detail 

 and elucidate their anatomical structure. He found that some 

 leaves, though externally agreeing with Phoenicopsis, were sufficiently 

 distinct in structure to be recognized as different genera. 3 One of 

 the new genera is Stephenophyllum, named after Cape Stephen on 

 the south coast of Franz Josef Land, where the specimens were dis- 

 covered. Seven narrow, straplike leaves are borne on a diminutive 

 axis surrounded at the base of the dwarf shoot by persistent bud- 

 scales. In appearance the foliage-shoot closely resembles a Phoeni- 

 copsis, but distinctive anatomical features are believed to justify the 

 institution of a new generic name. Another genus, Windwardia, 

 named after the ship Windward, chartered by the Jackson-Harmsworth 

 Expedition of 1896, whose members collected the material, bore 

 dwarf, deciduous shoots, each with five or seven linear leaves about 5 

 inches long, distinguished from those of other Ginkgoalean trees by 

 the absence of secretory ducts and by a few other anatomical pecu- 

 liarities. A third genus instituted by Florin is Culgoweria, a Scottish 

 type, so called after Culgower in Sutherland, a locality from which a 

 collection of Upper Jurassic plants, made by the late Dr. Marcus 

 Gunn, was described by myself in 1911. Leaves that were originally 

 assigned to Phoenicopsis on the ground of external resemblance have 

 now been examined microscopically and found to differ in certain 

 structural features from other members of the family. 



Dr. Florin's intensive study of the Franz Josef Land material 

 led to the discovery of two more genera in this arctic flora, Spheno- 

 baiera and Arctobaiera, both of which, as the names imply, are similar 

 in the external characters of the foliage to Baiera. Arctobaiera is 

 characterized by deeply divided tongue-shaped leaves borne in a 



•« A short account of Dr. Florin's admirable contribution was published in Nature, May 1, 1937. 



