409 
RECENT RESEARCHES ON THE JURASSIC PLANTS 
OF YORKSHIRE.* 
H. HAMSHAW THOMAS, M.A. 
SINCE the formation of the large collections of fossils from the 
Yorkshire coast by Williamson, Bean, Leckenby, and other 
enthusiastic collectors, few plant remains of importance have 
been obtained from this famous locality. In 1879 Professor 
Nathorst, of Stockholm, had obtained a number of new and 
interesting forms, and during a visit in 1909 he made further 
important discoveries, on which the first of his recent papers on 
Williamsonia was based. It became clear that much further 
information about the flora of Jurassic times might be obtained 
by renewed researches in Yorkshire, and the present paper is 
a brief summary of some of the results obtained by Professor 
Nathorst, Dr. T. G. Halle, and myself. 
Important additions to our knowledge of the Bennettitales 
have been made by Professor Nathorst. He distinguished, 
for the first time, the male sporophylls of Williamsonia, which 
are united together into a cup-like structure somewhat com- 
parable to a flower. The sporophylls are more or less covered 
with large sessile synangia from which the remains of the 
microspores can be extracted in great numbers by treatment 
with acid in the usual way. Waulliamsonia appears to have 
been unlike most of the Bennettites (or Cycadeoidea) in having 
unisexual ‘ flowers.’ Several species of male ‘ flowers’ have 
been distinguished, which differ in the number and the arrange- 
ment of the synangia. In some forms a considerable reduction 
in the number of synangia seems to have taken place. The 
female strobilus of Williamsonia bears a close resemblance to 
the corresponding structure in Bennettites. 
I have recently discovered near Gristhorpe a new Bennet- 
titalian ‘ flower’ which appears to be bisexual. The central 
axis bore the usual ovules and interseminal scales, and below 
this there was a whorl of five or six large free sporophylls, 
arranged in a similar way to the petals of a hypogynous flower. 
On these sporophylls five or six large reniform sporangia were 
borne. 
Some facts in the history of seed-bearing plants will pro- 
bably be furnished by the study of some small fruit-like bodies 
which I have recently found and have named Caytonia. They 
appear to contain the remains of eight to ten seeds, each I to 2 
mm. long, and similar isolated seeds have been obtained. 
A certain amount of their structure has been preserved, and 
parts of the integuments, nucells, and micropylar tubes can 
be made out. These fruits appear to be undoubtedly angio- 
* Read at the Portsmouth Meeting of the British Association. 
agi Dec. 1. 
