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Ruth Holden. 
that all specimens of Cycadites may have to be transferred to 
Pseudocycas, and the former genus abandoned. Such is the case 
with Saporta’s figures of C. rectangularis (2), and the specimens in 
the Sedgwick and British Museums confirm his description. 
Similarly, the midrib of C. Lonteti is figured as double, and in the 
text Saporta refers to the “ deux nervures longitudinales,” but 
concludes that this is a fake appearance, due to the condition of 
preservation. No comment is offered in the case of C. Delessei. 
Schenk (3) too, figures C. Roemevi with a double line, but refers to 
it as “ uninerva.” 
In this connection, it is interesting to consider the conditions 
obtaining in the living members of the genus Cycas. Here, of course, 
the midrib is unquestionably single, yet on the upper surface it 
usually appears as a ridge, bounded on each side by a furrow. 
(Text-fig. 1b). To facilitate the comparison, impressions were 
made from both sides of the leaf, on putty. In Plate III, Fig. 1 
represents the impression of the upper, Fig. 2 the lower side of a 
pinnule of C. siamensis, and it is evident that if fossilized, the former 
would be referred to Pseudocycas and the latter to Cycadites. As 
the leaves were allowed to dry, an interesting change took place. 
The ridge on the lower surface, which in the impression is represented 
by a single line (Fig. 2) collapses down the centre, forming a groove 
bounded on each side by a ridge. Text-fig. lc shows a cross 
section of a dried leaf; Plate III, Fig. 3 its impression on putty. 
If, as is probable, the analogy of living with fossil holds true, it is 
now easy to understand that the pinnules of P. insignis, P. Saportce, 
etc., have a double or a single midrib according as the impressions 
were made from the upper or the lower side of a fresh or a dried 
leaf. A careful comparison of Nathorst’s Tab. 1, figs. 3 and 5 with 
our Figs. 1 and 3 furnishes additional evidence that this explanation 
is the correct one. The two grooves on the upper surface of a leaf 
are always further apart than the two on the lower, the reason being 
that those on the upper are on each side of the midrib, while those 
on the lower are part of the collapsed midrib itself; and looking now 
at Nathorst’s fig. 5, where the pinnules are broken off, it is possible 
to see that the furrows of the upper side of the mumified plant, are 
more widely separated than those of the lower. We may conclude, 
therefore, that when it is a question of a mumified plant, there are 
always two grooves with a ridge between on the upper surface; and 
either a single ridge, or two ridges with a furrow between on the 
lower, according to the condition of the leaf when carbonised. 
