The Missing Link in Osmundites. 
BY 
rat 
MARIE CARMICHAEL STOPES, D.Sc., Ph.D, F.L.S., 
Fellow and Lecturer in Pqlaeobotany, University College , London. 
With Plate II and one Figure in the Text. 
I N their classic series of memoirs on the fossil Osmundaceae, Kidston and 
Gwynne-Vaughan say (Part II, 1908, pp. 229, 230) : ‘ the vascular anatomy 
of the Osmundaceae must be derived from a protostele with a solid cen- 
tral homogeneous xylem mass' and (in Part IV, 1910, p. 466) : ‘We regard 
the Osmundaceae, as a whole, as an ascending series of forms whose vascular 
system is to be derived from a primitive protostele with a solid homogeneous 
xylem.’ 
The missing link in the chain of practical evidence — that is to say, the 
actual species of Osmundites , possessing a solid stele and normal, simple 
Osmundaceous meristeles in the leaf-bases — was not known to them. The 
species about to be described from Australia fortunately shows this interest- 
ing conjunction of features ; and, writing to me about photographs of the 
new specimen I sent to him, Dr. Robert Kidston, F.R.S., said: ‘Your 
specimen seems to be the missing link we required.’ 
The specimen came to my hands, in the Geological Department of the 
British Museum of Natural Plistory, some years ago, having been most 
kindly sent to us, with other material, by Dr. Walcott, Director of the 
National Museum, Melbourne, Australia. At that time the British Museum 
was planning, not only to describe the British Cretaceous fossil plants (see 
Stopes, 1913 , 1915 ), but to prepare a complete comparative memoir on 
the Cretaceous plants of the whole world. As the war has rendered this 
project impracticable for many years to come, the present specimen seemed 
of sufficient interest to describe individually. 
I am much indebted to Dr. Walcott, of Melbourne, for permission 
to cut the specimen, and to Dr. Smith Woodward, F.R.S., Keeper of the 
Geological Department, for his unfailing help and courtesy in arranging 
for the section-cutting and other facilities for utilizing the material in 
his unique department. 
The specimen came with some others, all waterworn fossil woods, from 
Wollumbilla Creek, Queensland, described as ‘ probably Cretaceous ’. The 
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[Annals of Botany, Vol. XXXV. No. CXXXVII. January, 1921.] 
