VIII. On the spines, sporangia, and spores of Psilophyton princeps , Dawson, shown in specimens from Gaspé

Psilophyton princeps, though still incompletely known, is one of the most important Early Devonian plants, both on account of its morphology and of the place it occupies in the history of investigation of Pre-carboniferous vegetation. It was originally distinguished and described by Dawson from specimens collected in the Gaspé peninsula, Canada. As shown in the restoration, published in the ‘Geological History of Plants’ (DAWSON, 1882), he regarded the plant as consisting of horizontally growing rhizomes, from which sprang erect branch-systems; the branching was dichotomous and the fine distal ramifications terminated in large ovoid sporangia. From the description (DAWSON, 1871) it is clear that the lower portions of the sub-aerial branch-systems were markedly spiny, while the spines, though present, became less numerous and more distant in the distal, fertile regions. The distribution of the spines according to Dawson is not shown in his restoration; it is well illustrated in a modification of Dawson’s restoration by PIA (1926, fig. 109).