670 DR R. KIDSTON AND PROF. W. H. LANG ON OLD RED SANDSTONE PLANTS 
on main stems with small spine-like leaves. This, in our opinion, goes far to establish 
the organic connection of his Dawsonites arcuatus with Psilophyton princeps. 
We are not in a position to enter into a critical consideration of the plant of 
Psilophyton princeps as a whole. In estimating the well-founded objections 
mentioned above to Dawson’s reconstruction, it should be borne in mind that 
he had exceptional opportunities for considering the plant as preserved at Gasp6. 
Even if there is a considerable element of imagination in his reconstruction, it would 
appear that it represents with remarkable justice or prescience a particular type of 
plant characteristic of Early Devonian times. 
The remains of Asteroxylon go far to establish the existence of another plant of 
Old Red Sandstone age showing all the regions of Psilophyton as reconstructed by 
Dawson. The leafless rhizome with root-like branches, and the stems with small 
leaves and more or less lateral branching, are features of agreement dependent on 
definitely ascertained facts. So also are the smooth leafless axes with the sporangia, 
if these are rightly ascribed to Asteroxylon. The sporangia with terminal dehiscence, 
though of smaller size, have their counterpart in Psilophyton. 
The two reconstructions, though both admittedly imperfect, exhibit a corre- 
spondence that makes them mutally supporting. 
Some other Early Devonian plants may be considered in relation to the general 
type indicated by Asteroxylon and Psilophyton. Thus Arthrostigma agreed in the 
branched stems, with a central vascular strand, bearing pointed or spine-like leaves. 
Nothing is known of the subterranean parts of this plant, or of its reproductive organs. 
Pseudosporochnus, known from impressions in Bohemia, which are reterred to the 
Middle Devonian, appears to have consisted of a stem-system of large size with 
continued subdivision of its branches. Some of the fine ultimate branches end in 
swellings, which are doubtfully referred to sporangia by Potonie and Bernard.* 
There is no evidence of the existence of leaves in this plant, and the subterranean 
organs are unknown. 
The crowded arrangement of the small leaves on the branched stems of 
Thursophyton ( Lycopodites ) Milleri, from the Middle Devonian of Scotland and 
Norway, suggests comparison with Asteroxylon. Nothing is known of the repro- 
ductive organs of Thursophyton. In this connection the prevalence of a number of 
types of land-plants of moderate size in the Middle Devonian flora of Norway, as 
described by Nathorst,| may be referred to. One of these, Broggeria Norvegica , 
seems worthy of consideration in relation to the possible fertile region of Asteroxylon. 
From Nathorst’s figures * the plant may have had terminal fertile regions with 
crowded sporangiophores, and not a definite cone. 
In another direction comparison may be extended to certain frond-like remains 
without any flattened lamina or pinnules ( Aphyllopteris , etc.) common in Middle 
* Flore Devonienne de Vintage H. de Barrande, p. 32, figs. 71-72. 
f Nathorst, “Zur Devonflora des westlichen Norvegens,” Bergens Museum Aarbok, 1914-1915, No. 9. 
X Ibid., Taf. 3, figs. 5-7 ; Taf. 4, figs. 4-9. 
