XXl] OSMUNDACEAE 337 



culata, a common type of leaf which was found also in association 

 with the slightly older New Zealand stem, Osmundites Dunlopi. 



An examination of the internal structure of the South 

 African stem by Dr Kidston and Mr Gwynne-Vaughan has 

 revealed many interesting features, which will be fully described 

 in Part IV. of their Monograph on fossil Osmundaceous stems. 

 I am greatly indebted to these authors for allowing me to 

 publish the following note contributed by Dr Kidston: — 



" The section oi Osmundites Kolhei Seward, shown in fig. 255, 

 presents the usual appearance of an Osmundaceous stock. The 

 parts contained in this section are the stele, inner and outer 

 cortex and a portion of the surrounding mantle of concrescent 

 leaf-bases. The whole specimen has suffered much from pressure, 

 but if restored to its original form the xylem ring must have 

 been about 19 mm. in diameter. The number of xylem strands 

 is about fifty-six and several of them are more or less joined 

 as in the modern genus Todea. The tracheae are of the typical 

 Osmundaceous type, that is to say, the pits are actual perfora- 

 tions and several series of them occur on each wall of the larger 

 tracheae. 



The most interesting structural characteristic of Osmundites 

 Kolhei is not well seen in the figure owing to the compression 

 of the xylem ring. This consists in the occurrence of tracheae 

 in the pith. In fact, we have here a mixed pith, composed 

 of parenchyma and true tracheae, a condition which connects 

 the Osmundaceae with a parenchymatous medulla with those 

 possessing a solid xylem stele like Zalesskya and Thamnopteris 

 and so completes the series of transitions extending from the 

 older and solid-steled forms to the modem medullated members 

 of the Osmundaceae." 



Osmundites skidegatensis, Penhallow. 



This lower Cretaceous Canadian species, first described by Pen- 

 hallow^ and more recently by Kidston and Gwynne-Vaughan 2, is 

 remarkable for the large size of the stem, the stele alone having 

 a diameter of 2'4 cm. Penhallow figures a fragment of a leaf 

 1 Penhallow (02). ' Kidston and Gwynne-Vaughan (07). 



