Conducting Tissue-System in Bryophyta. 37 
EXPLANATION OF FIGURES IN PLATES I AND II. 
Illustrating Mr. Tansley’s and Miss Chick’s paper on the Conducting 
Tissue-System in Bryophyta. 
PLATE I. 
Section I. The Conducting Strands of Liverworts. 
Fig. 1 . Transverse section of midrib of thallus of Pallavicinia hibernica (Hooker), 
S. F. Gray, Wilsoniana, Carrington, from Malahide, co. Dublin, showing two 
lateral strands of thin-walled but lignified, probably water-conducting cells, x 48. 
Fig. 2. Part of longitudinal section of the same, passing through one of the 
strands ; showing elongated, slightly prosenchymatous shape, and scanty dis- 
organized contents of the strand-cells. At a , very thin cross-wall in a long strand- 
cell. The lignification extends to parts of the walls of the neighbouring cortical 
cells, x 50. 
Fig. 3. Transverse section of midrib of thallus of Pallavicinia Lyellii (Hooker), 
S. F. Gray, showing central strand of narrow thick-walled hydroids, and a few 
rhizoids on ventral surface, x 1 10. 
Fig. 4. Parts of hydroids of Pallavicinia decipiens , Mitten, showing the often 
irregularly scattered pits. These are oval or elongated in surface view, with their 
long axes perpendicular to the long axis of the cell, or more often slightly inclined, 
so that the pits are arranged on imaginary spirals running round the cell. In section 
they are seen to be normal deep simple pits. Where a hydroid abuts on a cortical 
cell (left-hand hydroid and left-hand wall of right-hand group) the thin wall of the 
latter is quite unpitted, while the wall of the hydroid may be richly pitted. oil 
immersion, x 500. 
Fig. 5. Transverse section of midrib of thallus of Symphyogyna sinuata (Sw.), 
Mont, et N., showing rhizoids on ventral surface of thallus and weak central hydrom- 
strand. x 100. 
Fig. 6. Transverse section of midrib of thallus of S. Brasiliensis (N. ab. E.), 
Mont., showing absence of rhizoids and bulky strand with cells of larger diameter 
at the periphery. x 100. 
Fig. 7. Diagram of transverse section of frond-stalk of S. rhizobola , showing 
relation of diameter of bulky strand to that of whole stalk. 
Fig. 8. Transverse section of rhizome of the same, showing rhizoids and relatively 
weaker strand, x 100. 
Fig. 9. Transverse section of comparatively weak rhizome-strand of Hymeno- 
phyton Phyllanthus (Hooker), Dum. x 145. 
Fig. 10. Transverse section of bulky band-shaped strand of frond-stalk of H. 
Jiabellatum (Hooker), Dum. x 100. 
Fig. 11. Upper part of midrib of leaf of Diplophyllum albicans (L.), Dum., 
in surface view, showing elongated cells of rib with sparsely and very irregularly 
pitted walls and much fewer chloroplasts than the square cells forming the rest of 
the leaf, x 200. 
