Affinities of the Palaeozoic Seeds of the Conostoma Group. 31 
state of preservation is as a rule inadequate to show the nature of the cell- 
walls ; however, as at least one cell of the lagenostome bears distinct traces 
of sculpturing, it may be regarded as probable that in this respect also 
our seed was in agreement with Conostoma oblongum. 
7. The Plinth. 
The wall of the plinth survived as a carbonized crust, much as we find 
it in the poorer specimens of Conostoma oblongum. At its summit a similar 
depression was present, corresponding with the insertion of the lagenostome 
(Figs. 25, 29, and 30). The close relations already noted in the case of 
Conostoma oblongum between the plinth and lagenostome on the one hand, 
and the plinth jacket and micropylar funnel on the other, repeat themselves 
here in all essentials, even including the well-marked sinus just above the 
region at which nucellus and integument were confluent (cf. PL II, Fig. 14, 
and PI. Ill, Fig. 29, s.). 
The contents of the plinth are represented by the same structures as in 
Conostoma oblongum. From the base of the lagenostome the ‘ lens ’ hung 
suspended (PI. Ill, Fig. 29, Is.), and below it in the same figure is found 
the pad of tissue which adhered to the tapetal septum ( pd .). In specimen 
J. 9 the ‘ lens 5 is slightly displaced, but its primitive position is still indi- 
cated by a connecting shred of membrane (Fig. 25, Is). Pollen-grains are 
present in the plinth cavity of specimens J. 9 and J. 12 (Figs. 25 and 24 ,pg). 
Their average dimensions are 85 M x 75 jut — somewhat in excess of those 
for the companion species. 
Very distinct traces of a tapetum enclosing the megaspore chamber are 
present (Fig. 31), but the character of the preservation hardly warrants 
detailed description. At the micropylar end the tapetum stretches across 
the nucellus as a septum, delimiting the base of the plinth (Fig. 30). 
IV. Comparison with Related Types. 
Comparison with Gnetopsis elliptica . 
This famous seed was described and illustrated with some fullness by 
Renault in 1884 from specimens discovered in one of the Grand’Croix 
nodules. 1 Apart from the supposed relations with the Gnetales, Gnetopsis 
remained for many years a very isolated type until the reinvestigation of 
Lagenostoma revealed the existence of certain features which these two 
seeds appeared to have possessed in common. 2 
With Conostoma oblongum the points of agreement are numerous and 
striking, and demand some notice here. 
1 Renault : Cours de Bot. fossile, vol. iv, p. 180, PI. XX, XXI, XXII. 
2 Oliver and Scott : On Lagenostoma Lomaxii. Phil. Trans. B., vol. cxcvii, p. 233. 
