6io 
Notes . 
Diploxylon stems from Halifax and Oldham, and the Lepidodendroid 
stem from Burntisland, shows that the primary xylem becomes 
broader in this series of forms. The polar groups of small elements, 
which still form strongly prominent teeth on the surface of the 
corona in the stems from Halifax and Oldham, are considerably 
reduced in the Burntisland plant, just as in Lepidodendron selaginoides. 
The leaf-trace, which is still given off from the middle of a sinus in 
the Halifax and Oldham stems, arises laterally, in relation to the teeth 
of the corona, in the Burntisland stem, approaching Lepidodendron 
selaginoides in this point also. The secondary wood of the Burntisland 
form shows no indication of any differentiation of the secondary wood 
into segments or arcs corresponding to the sinuses and teeth of the 
primary wood. In fact, certain English types of Diploxylon only 
accentuate the differences which separate the Haidinghen Sigillaria 
from S. spinulosa. 
The central axis of the ribbed Sigillaria differs from that of the 
Phanerogamic type in the manner of origin of the leaf-traces and 
in the structure and centripetal development of the primary xylem ; 
these structural features characterize the radial form of vascular axis, 
and are in short those of a well-defined Cryptogamic type. 
THE JURASSIC FLORA OF BRITAIN h— The Jurassic plant- 
bearing strata exposed in the cliff sections of the Yorkshire coast, 
between Whitby and a few miles south of Scarborough, have afforded 
unusually rich data towards a restoration of the characteristics and 
composition of a certain facies of Mesozoic vegetation. Since the 
publication of A Geological Survey of the Yorkshire Coast, by 
Young and Bird, in 1822, the numerous species of Inferior Oolite 
plants from Gristhorpe Bay, Scarborough, Cloughton Wyke, Haiburn 
Wyke, Whitby and other localities have been described by Phillips, 
Brongniart, Bindley and Hutton, Morris, Goppert. Leckenby, Saporta, 
Zigno, Nathorst, Carruthers and other writers, but no detailed account 
of the flora has been published. The names of Bean, John Williamson, 
his son William Crawford Williamson, Phillips, Murray, Leckenby and 
others will always be closely associated with the earlier investigations 
of the fossil flora of east Yorkshire. The British Museum unfortu- 
nately possesses but few of the type-specimens of these Jurassic plants ; 
1 Read before the Botanical Section of the British Association, Dover, Sept. 1899. 
