FALL A VICINIA . 437 



conducting, though water passes through it much more slowly 

 than is the case in mosses. In P. hibernica from Malahide, which 

 Mr. McArdle sends me, we find two lateral strands of very thin 

 walled but distinctly prosenchymatous cells which may be water 

 conducting, but not having living material I cannot tell for 

 certain. In larger plants from Lough Bray {Jun(/. hibernica, 

 Hook. Brit. Jung, type) we can find no trace of such strands, 

 neither can we in the specimens you sent from Coatham Marshes, 

 Yorkshire, Wm. Ingram (var. Wihoniana). "... there is the 

 occurrence in the Malahide plant of two distinct lateral veins in 

 the mid-rib. The walls of the cells of these veins are distinctly 

 lignified though very little if at all thickened, and in other 

 respects, so far as can be seen from dried material, the strands are 

 rudimentary compared with that of P. Lyellii and other species ot 

 Pallavicijiia, Si/mpho(///jia, &c. I shall, of course, be glad to know 

 if you find other characters in the Malahide plant distinguishing 

 it from true P. hibernica, but even if not, the marked anatomical 

 characters I find seem to me to justify its separation as a distinct 

 species. In the absence of more conspicuous external characters I 

 would suggest leptodesma as a specific name in allusion to the 

 rudimentary character of the strands." For an account and 

 figures of these strands see Tansley and Chick, " Notes on the 

 Conducting Tissue System in Bryophyta," Annals of Botany, 

 Vol. XV., March, 1901. 



Description of Plate CXCII. — Fig. 1. Plant natural size 

 (Hooker). 2. Frond x ? (ditto). 3. Cross-section of midrib x 

 24 (Lough Bray, McArdle). 4. Portion of frond x 290 (var. 

 Wiho7iiana), (Hayle, Curnow). 5. Portion of bract and perianth 

 X ? (Hooker). 6. Portion of bract and pistillidia x 24 (Lough 

 Bray, McArdle). 7. Capsule x ? (Hooker). 8. Portion of male 

 frond X ? (Hooker). 



Description of Plate CXCIII. — Fig. 1. Plants natural size 

 (var. leptodesnia), (Malahide, McArdle). 2, 3. Ditto (var. IFilsoniana), 

 (Aberffraw, Wilson). 4. Plants slightly enlarged (ditto). 5. 

 Fertile plant x 11 (var. leptodesma), (Malahide, McArdle). (5-8. 

 Cross-sections of mid-rib x 24 (ditto). 9. Perianth x 11 (var. 



