230 
Weiss. — A Stigmaria zvith Centripetal Wood. 
Williamson, W. C. (’87). A Monograph on the Morphology and Histology of Stigmaria jicoides. 
Memoirs of the Palaeontographical Society, 1887. 
(’ 89 ). Organisation of the Fossil Plants of the Coal Measures, Part xvi. 
Phil. Trans., 1889. 
Weiss, F. E. (’02). The Vascular branches of Stigmarian rootlets. Annals of Botany, vol. xvi, 
No. LXIII, 1902. 
(’07). The Parichnos in the Lepidodendraceae. Memoirs of the Manch. Lit. and 
Phil. Soc., vol. li, 1907. 
EXPLANATION OF PLATE XV. 
Illustrating Professor Weiss’s Paper on Stigmaria. 
Fig. 1. Transverse section of Stigmaria , showing the central cylinder with secondary 
thickening surrounded by the wide periderm layer (peri) which has been much compressed and 
is thrown into folds. The border of the periderm has been outlined with Indian-ink to render it 
more distinct. Slide R. 881 b magnified, x 2^. 
Fig. 2. Enlarged view of central cylinder, showing the centripetal primary wood (p . wi) sur- 
rounded by mantle of secondary wood (s. wi) ; at the upper edge of the central cylinder a rootlet 
bundle is passing to the exterior. Q. 403 A. x 24. 
Fig. 3. Tangential longitudinal section through the secondary wood, showing rootlet bundle 
(r. b.) on its way to exterior. R. 881 i. x 42. 
Fig. 4. Tangential longitudinal section through the secondary wood, showing the medullary 
rays (m. ri), and a rootlet bundle (mesarch) in the centre of the photograph, s. r. = scalariform 
tracheid. R. 881 x 46. 
Fig. 5. Transverse section at the outer boundary of central cylinder, showing two lateral 
mesarch bundles (r. bi) with centric arrangement of secondary tracheids. The tracheids of the 
lateral branch are much smaller than those of the secondary wood (s. wi) of main axis. R. 881 c. 
x 100. 
Fig. 6. Transverse view of lateral bundle (1 v.b . ) in the region of middle cortex, showing its 
connexion with a patch of reticulate tracheids (r. /.). R. 881 h. x 100. 
Fig. 7. Lateral vascular bundle (v. b.) in region of middle cortex, showing characteristic con- 
strictions and connected with a large patch of wide reticulate tracheids (r. ti). R. 881^. x 40. 
Fig. 8. Portion of longitudinal section of periderm (per.) through which a vascular bundle (v. bi) 
is passing to rootlet cushion (defective), par. = parichnos strand of parenchymatous cell running 
below the rootlet bundle. R. 881 i. x 30. 
