2 i 8 Seward. — On Rachiopteris Williamsoni sp. nov. 
with any other living plants. It would be unwise to definitely 
include it in that family ; the evidence at our command is far 
too incomplete, and it is probable that those peculiarities of 
structure which have been described in the fossil petiole are of 
sufficient importance to exclude it from any existing family. 
I have ventured to adopt the specific name Williamsoni as 
a slight recognition of the encouragement and generous help 
which I have always received from Prof. Williamson. 
EXPLANATION OF FIGURES IN PLATE XIII. 
Illustrating Mr. Seward’s paper on Rachiopteris Williamsoni. 
The numbers in brackets refer to Prof. Williamson’s Catalogue of his private 
collection. 
Fig. i. Transverse section of the outermost cells of a petiole, showing the 
epidermal layer ep. x 175. (C. N. 278.) 
Fig. 2. Transverse section of a petiole of R. Williamsoni : h, hypoderm, nat. 
size; a, parenchymatous tissue and secretion? sh , section of a shell. (C. N. 282.) 
Fig* 3 * Canal with stereome. x 175. (C.N. 282.) 
Fig. 4. Single vascular bundle near the periphery of the petiole. X37. (C. N. 
282.) 
(For this photograph, and that reproduced in Fig. 5, I am indebted to Mr. C. A. 
Barber.) 
Fig. 5. Single bundle: p, protoxylem ; c, c , bundle- canals. X37. (C.N. 282.' 
Fig. 6. Single bundle : c, c 1 and c n , canals, x 37. (C. N. 282.) 
Fig. 7. A larger vascular bundle : c iU -c yi , canals ; p, protoxylem ; p\ ? proto- 
xylem. X37. (C.N. 282.) 
Fig. 8. Single large bundle : s, space close to protoxylem ; c . . ., bundle-canals. 
X37 . (C.N. 282.) 
Fig. 9. Longitudinal section of a vascular bundle : a, xylem-parenchyma ; 
ph, cambiform phloem-elements ; c, bundle-canal; b, crack in crystalline substance 
fdling up canal ; f, fundamental parenchyma ; g , large canal ; in , stereome-strand ; 
n, sac. X37. (C. N. 284.) 
Fig. 10. Longitudinal section of the protoxylem of a bundle : p , protoxylem ; 
t, scalariform tracheid. x 175. (C. N. 285.) 
Fig. 11. Two canals, r 1 ' 1 ' and r 5v of Fig. 7. x 1 75 - 
Fig. 12. Two more canals, c y , c vi of Fig. 7. X175. 
Fig. 13. Three canals, c vii , c viil , c H , of Fig 6. x 175. 
Fig. 14. Transverse section of Angiopteris evecta, var. Teysmanniana , showing 
a single vascular bundle with large sieve-tubesv in the phloem : sv, sieve-tubes. 
