CUTICULAR STRUCTURE OF PSILOPHYTON. 385 
is no evidence that the highly euticularised spines are homologous with the 
traumatic intumescences of Rhynia, and they differ from the slightly larger 
and less spine-like leaves of Asterozylon, with which a closer comparison is 
possible, in the absence of stomata. 
REFERENCES. 
ARBER, E. A. N. 1921. Devonian Floras. Cambridge. 
Dawson, J. W. 1871. The Fosail Plants of the Devonian and Upper Silurian Formations 
of Canada. Rep. Geol. Surv. Canada. 
Haute, T. G. 1916. Lower Devonian Plants from Roragen in Norway. K. Svensk. 
Vetenskapsakad. Handl. Bd. 57, no. 1. 
Kivstox, R., & Lane, W. H. 1917. On Old Red Sandstone Plants showing Structure 
from the Rhynie Chert Bed, Aberdeenshire, Part I. Trans. Roy. Soc. Edin. 
vol. li. pp. 761-784. 
—— — 1920. Ibid. Parts II. & II]. Ibid. vol. lii. pp. 603-627, 643-880. 
—— 1921. Ibid. Parts IV. & V. Ibid. vol. lii. pp: 831-902. 
WALTON, J. 1923. On a new Method of Investigating Fossil Plant Impressions or Incrus- 
tations, Ann. Bot. vol. xxxvil. pp. 379-301, 
Ware, D. 1905. (In Smitu & Wuire.) The Geology of the Perry Basin in South- 
eastern Maine. U.S. Geol. Surv. Prof. Paper no. 35. 
EXPLANATION OF PLATE 37. 
Fig. 1. Psilophyton princeps Daws. Gaspé, Canada, $ nat. size. Brit. Mus. Geol. Dept., 
no. V. 18233. Photo H. G. Herring. 
. P. princeps. Cuticle with stomata taken from the fragment shown in text-fig. 1. 
x 52, Slide V. 14918c. Photo J. H. Leonard. 
2. P. princeps. Another portion of the same cuticle, showing papille. x75. 
Photo F. W. Edwards. 
6. P. princeps. A single stoma from the same slide. x 240. Photo F. W. Edwards. 
5. Asteroxylon Mackiei Kidst. & Lang. Rhynie Chert, Old Red Sandstone, A berdeen- 
shire. Epidermis with stomata. x 30. Slide V., Brit. Mus. Geol. Dept. Photo 
F. W. Edwards. 
4. A. Mackiei. Part of the cuticle shown in fig. 5. x 60. Photo F. W. Edwards. 
CS 
le 
