REPORT OF THE CHIEF ASTRONOMER 815 



SESSIONAL PAPER No. 25a 



While, therefore, it is not altogether possible to establish specific identity between 

 the two, there is little reason to doubt that G. gilbert- thompsoni is the modern 

 representative of P. arborescens. 



Directing comparisons to Tertiary forms, it is found that the genus is but 

 sparingly represented in that age. Pecopteris torellii of Heer, is an element of 

 the Eocene flora of Unga island (42), while it is also common to the Miocene 

 of the island of Saghalien (21), but as this plant can no longer be regarded as 

 one of the Gleicheniacese, but rather, as Lesquereux points out, a true Osmunda, 

 it must be excluded from further discussion in this connection. 



Perhaps the nearest representative of this type is to be found in Gleichenia 

 zippei, Heer, from the Kome beds of Greenland (35: p. 44, pi. iv., v., vi., vii.). 

 While there is a general resemblance which unquestionably brings the two 

 into generic relation, there are important differences in the length and shape 

 of the pinnules which definitely establish a specific difference. 



We are thus brought to a comparison with the geologically most recent 

 of all known species — P. sepulta, Newb. This plant was described by Newberry 

 in 1882 (45) as having been obtained from the Eocene of Green river, Wyoming. 

 No figure is given, but the description shows the pinnules to be confluent, united 

 by one-third of their length, slightly curved upward and flabellate on the upper 

 side. 



It is thus clear that P. sepulta is not even remotely related to the one under 

 discussion, and from the evidence collected, the latter must be regarded as 

 altogether a new one, for which a definite name is demanded. But since the 

 above was written, a copy of Ward's latest contribution to our knowledge of the 

 Mesozoic flora has come to hand (57:616), and in this way my attention was at 

 once drawn to a description and figures of Gleichenia gilbert-thompsoni, as 

 originally described by Fontaine, as being at least closely similar to the Skagit 

 river specimen. Unfortunately, Ward gives no detailed description of this speci- 

 men, a fault which equally applies to most of the other specimens dealt with, 

 and one is obliged to rely wholly upon the figure which, fortunately, is most . 

 excellent and apparently of normal scale. Careful measurements of the figure 

 give the following diagnosis : — 



Frond twice pinnate: pinnae 1 — 1-2 cm. distant and inserted at angles of 

 55° — 60°, more than 6-5 cm. long and linear within that limit, 11 mm. broad. 

 Pinnules crowded, more or less contiguous but wholly distinct, attached by the 

 full width of the broad base; not decurrent; 6 mm. long and 3:5 mm. wide; 

 oblong-linear and abruptly rounded at the broad apex; inserted at angles ranging 

 from 67° — 90°, with intermediate variations resulting from displacement; only 

 the central midrib shown. 



A comparison of this diagnosis with that for the Pasayten river specimen 

 will at once show that the only essential difference between the two lies in the 

 size of the pinnules — a difference which may well belong to different parts of 

 the same frond. It is thus possible to conclude that our specimen is identical 

 with Fontaine's species. 



