59 
Stopes. — The Missing Link in Osmundites. 
The leaf-base is, as has already been mentioned, quite normal and 
typical for the Osmundaceae. An enlarged photo of the portions within 
the sclerized ring and the complete meristele are shown in Photo 6 , and 
a diagram of the whole, showing the position of the sclerotic nests , is given 
in the Text-fig. In the detailed cellular structure of the leaf-bases of the 
new plant no feature meriting special description occurs. The xylem, 
phloem, and other tissues are apparently entirely usual for the leaf-bases of 
this family. 
The roots , of which many are to be seen cut in a variety of directions 
in among the leaf-bases, are also typical for the family. Their stele is 
diarch , with a group of about a dozen tracheides and a well-marked sheath. 
See Photo 7, PI. II. In longitudinal oblique sections, which are numerous, 
the tracheides appear to be provided with series of irregular rows of narrow 
pits. They appear to answer to the following description : ‘ The tracheae 
are of the typical Osmundaceous type ; that is to say, the pits are actual 
perforations, and several vertical series of them occur on each wall J 
(Kidston and Gwynne-Vaughan, 1910, p. 456). 
Diagnosis. 
As strict comparative diagnoses have not been given for the various 
species of the group, even in the Kidston and Gwynne-Vaughan Memoirs, 
it is more difficult than it inevitably need be to diagnose a new species from 
a single and incomplete specimen. Whether or not its small size is charac- 
teristic is hard to say; as the secondary wood of the axis was already 
forming, this may be a specific feature worth including in the diagnosis. The 
plant described above is named in honour of Dr. R. Kidston, F.R.S., 
of Stirling, who has done such unique work in Palaeobotany, and has 
specially interested himself in this group : 
Osmundites Kidstoni, sp. nov. 
General type of the vegetative body characteristic of the genus ; leaf- 
bases and roots typical, but main axis a protostele with secondary wood. 
Roots diarch, adventitious among leaf-bases. Leaf-bases with a simple bow- 
shaped meristele, embracing a sclerenchyma patch in each curved end, and 
surrounded by a ring of sclerenchyma ; irregular lateral sclerenchyma 
patches in the lateral wings of the leaf-base. Main axis apparently solid, 
roughly circular, made up of somewhat stellate, seven-rayed protostele 
filled in with bays of secondary wood. Tracheid diameter varying between 
1*5 fjL and 3 /I. Stele surrounded by a sheath of dark cells. The whole plant 
very small, measuring less than 2 cm. from the centre of the stele to the 
largest and outermost leaf-base. The largest leaf-bases measure approxi- 
mately only 3-4 mm. across the ring of circumstelar sclerenchyma. 
Locality . Wollumbilla Creek, Queensland. 
