TRANSACTTOTirS OF SECTION K. 847 



tissues : (e) tlae influenco of latPral pressure ; (/) tho difference for different 

 fluids. 



4. On tlie Anatomy of Todea, toith an Account of the Geolor/ical History 

 of the Osmundacea'. By A. C. Srward, F.R.S., and Miss Sybille 

 6. Ford. 



The anatomical structure of the genus Osmunda has been dealt with by several 

 ■writers, and more particularly by Zanetti in an able paper published in the 

 'Botanische Zeitung' for 1895, but the other genus of the Osmundaceje has not 

 received equal attention at the hands of anatomists. Our work, which was under- 

 taken with a view to discover in what respects Todea differs from Osmunda, 

 includes the examination of Todea harbara and T. sujierba, as well as the investi- 

 gation of series of microtome sections of young plants. The family Osmundace.ie 

 is usually regarded as to some extent intermediate between the Eusporaugiate 

 and Leptosporangiate ferns, and in many respects the two genera Osmunda and 

 Todea are of interest in regard to the phylogeny of the various divisions of the 

 Filicinas. 



The stem of Todea Barbara is traversed by a single stele composed of xylem 

 groups surrounduig a central pith and separated from one another by medullary 

 rays : these groups vary considerably in shape and number at different levels. There 

 may be as few as two or as many as eight xylem strands in one transverse section 

 of tlie stem, while in Osviimda reualis the number is considerably gi'eater. The 

 xylem strands are surrounded by parenchyma, and the sieve-tube zone occupies 

 the same position as in Osmunda. This zone, which is continuous in 0. regalis, is 

 occasionally discontinuous in Todea opposite some of the xylem strands. The 

 comparatively large sieve-tubes occur in triangular patches at the outer end of 

 each medullary ray. A characteristic band of tangentially elongated elements 

 succeeds the sieve-tube zone, and this is followed externally by a parenchymatous 

 band, the outermost layer of which constitutes the endodermis. The paper deals 

 with the phyllotaxis of Todea harbara, the origin of the leaf- traces, and the gradual 

 alteration in structure which the collateral leaf-trace undergoes as it passes out from 

 the stele of the stem as a horse-shoe shaped strand with one protoxylem group 

 and gradually assumes the form of the broadly U-shaped concentric stele of the 

 petiole with its numerous protoxylem groups. The anatomy of 'seedling' plants 

 of Todea is found to agree with that of Osmunda reyalis plantlets as described by 

 Leclerc du Sablon. As bearing on the questions of relative antiquity and phylogeny 

 of tlie members of the Filices, we have endeavoured to give an account of the 

 geological histor}' of the Osmundaceae. 



5. The Glossopteris Flora of Australia. 

 By E. A. N. Arber, B.A., Trinity College, Cambridge. 



The Glossopteris flora is one of the most remarkable and widely distributed of 

 fossil floras. Typical members, such as the fern-like plants Glossopteris and 

 Gangatnopteris, with the Equisetalean genus Fhijllothe.ca, occur in rocks of 

 Permo-Oarboniferous age in India, Australia, South Africa, and South America, 

 pointing to the former existence of a southern continent whose flora was for the 

 most part distinct from that of the same age in Europe and North America. 



In the Newcastle beds of New South "^^'ales all the typical members of the 

 flora occur without any admixture of nortlicrn types (e.g., Lepidodendron and 

 Sif/illaria), as has been recorded from similar beds in South Africa and South 

 America. The flora of the Newcastle rocks is interesting botanically both on 

 account of the wide distribution of the chief members, which show points of 

 identity and unity in type with those of the Lower Gondwana of India and the 

 Permian of Russia, and also from the morphological characters presented by many 

 of the plants themselves. Tho collection, which forms the subject of these 

 remarks, is in the Geological Museum, Cambridge, and is noteworthy as being one 

 of the earliest (1839-44) formed of fossil plants from the continent of Australia. 



