36 Oliver and Salisbury. — On the Structure and 
filling tissue in the former being reduced to a mere parenchyma sheath 
accompanying the vascular strands into the loculi. 
A peculiarity of Conostoma oblongum was the soft tissue at the apex of 
the integument, of which no indications have been detected in Lagenostoma. 
In both genera the integumental units show a high degree of coalescence 
in the micropylar region, the degree of fusion being considerably greater 
however in Lagenostoma than Conostoma, which appears somewhat to 
approach the condition of Lagenostoma (. Physostoma ) Kidstonii , Arber. 1 
This coalescence of integumental units may be regarded as yet another 
example of a generally diffused tendency, no doubt correlated with a 
simplifying of the mechanism of development, viz. the replacement of separate 
parts borne at the same height by a continuous structure. 
The lagenostome of Lagenostoma reaches the exterior of the seed 
by a tubular prolongation, thus contrasting markedly with the etubular 
condition of Conostoma , where a functional micropyle is provided on the 
lines of most existing Gymnosperms. In view of this difference, it is not 
possible to regard the two types of seed as very closely related. 
Other contrasting features include the nature of the wall sculpturings 
of the lagenostome — which are not reticulate in Lagenostoma ; its relatively 
large size and the persistence of a central core of tissue — not yet detected 
in Conostoma . 
The plinth, which was present in full-sized seeds of Lagenostoma but not 
in the small ones (Text-fig. 12), sloped up at a very gentle angle as com- 
pared with the corresponding part of Conostoma ; its presence being corre- 
lated rather with a transverse than with a material longitudinal expansion 
of the nucellus. A ‘ tent-pole ’ does not appear to have been produced. 
Thus it is plain that whilst both Conostoma and Lagenostoma have pro- 
ceeded along similar lines in the coalescence of the integumental units, 
they show considerable divergence in the details of lagenostome structure, 
in the plinth, and in the arrangements for the reception of the pollen. 
V. Classification and Diagnoses. 
In the light of the previous discussion it is convenient to separate the 
various seeds that have been enumerated into three series or types, all 
of which possessed in common — 
(1) A nucellus and integument confluent up to the level of the plinth ; 
(2) a free part of the integument consisting either of separate lobes, or 
of a more or less completely fused series of lobes forming what has been termed 
a ‘canopy’ ; (3) a vascular system of strands running in the deeper parts of 
the integument and passing into the lobes or their representatives at the 
apex ; (4) an epidermis to the testa which was mucilaginous, at any rate 
E. A. N. Arber : On some New Species of Lagenostoma. Proc. Roy. Soc., B., vol. Ixxvi. 
