32 
Oliver and Salisbury . — On the Structure and 
The lagenostome of Gnetopsis has essentially the same form and in- 
sertion as in Conostoma . It is a small goblet-shaped body resting in 
a depression of the plinth with which its cavity became continuous. 1 The 
cells of its wall constitute only a single layer, so far as we can judge from 
the specimens, but they show evident traces of sculpturing like that of 
Conostoma , though less well preserved. 
Our examination of Renault’s original type specimens shows that the 
presence of papillae around the mouth of the pollen-chamber in the pre- 
parations B. 230, C. 2 and 11 (‘ languettes disposees en couronne ’) is to be 
interpreted as the result of partial resolution of the wall cells of the lageno- 
stome by means of fissures corresponding in position with some of the 
vertical lines which, as in Conostoma , separated the adjacent rows of 
sculptured cells. The resulting lobes or finger-like packets, which included 
as a rule two or three vertical series of these cells, remained attached below 
to the summit of the plinth. 2 
The dimensions of the lagenostome in the three seeds are as follows : — 
Gnetopsis. 
Maximum width 210 fi 
Width of basal orifice 1 15 /x 
Height 145 
C. oblongum. C. anglo-germanicwn. 
230 /x 260 /x 
180 fx 190/* 
150/x 190/x 
The agreement with Conostoma is complete when the nature of the 
lobing in Gnetopsis is apprehended. 
The Plinth. The broad low cavity between the prothallial chamber 
and the lagenostome corresponds with the plinth of Conostoma. It was 
naturally termed the ‘ pollen-chamber * by Renault as it is here that the 
pollen is usually found. 3 * * The central portion of its cavity is occupied by 
a plug of tissue which rests on the floor, much as in our C. oblongum , 
specimen R. 117 (PI. II, Fig. 16). Occasionally in Gnetopsis (B. 230, 
C. 12) this somewhat robust lump of tissue is produced towards the lageno- 
stome into an upwardly directed, more delicate continuation. It is hardly 
possible to say whether the latter alone represents the displaced central 
core of the lagenostome whilst the lump below is the residual tissue of the 
plinth, or whether both may not have been derived from the lagenostome- — 
a difficulty also found in the interpretation of our R. 117 (cf. p. 22). 
1 Renault : loc. cit., PI. XXII, Fig. 4. 
2 In Renault’s preparations the lagenostome occurs under two types of preservation, i. e. the 
fingered or papillose type (which we interpret as macerated) represented in Cours de Bot. foss., vol. iv, 
PI. XX, Fig. 3, and PI. XXI, Fig. 3,0, and the intact type represented on his PI. XXII, Fig. 4,/ 1 . 
The information, for which we are indebted to Prof. Bertrand, that the intact type (which differs 
slightly in other respects) was probably derived from a source other than Grand 7 Croix (which 
provided the main series of specimens) explains the differences referred to. 
3 In all the specimens of seeds of the Conostoma group that have passed through our hands we 
have only detected a single pollen-grain in the lagenostome, viz. in Gnetopsis t the specimen being 
the one figured by Renault on his PI. XXI, Fig. 4. 
