an archaic type of Seed from the Palaeozoic Rocks . 109 
that no direct evidence of continuity with vegetative organs has come to 
light during the course of the investigation, nor have any traces of such 
structures as a cupule or stalk been detected which might have served 
indirectly, as in the case of Z. Lomaxii , to establish such a connexion. 
The relationship with the Lagenostoma-g roup depends upon essential 
similarity in organization between Physostoma and those seeds. 
This agreement was evident to Williamson, who thirty years ago had 
— B 
— C 
Text-fig. io. Diagrammatic longitudinal and transverse sections of Lagenostoma Lomaxii. 
The letters A, B, C, and D show the heights at which the transverse sections are cut. The hard 
outer layer of the seed-coat is drawn in black; the soft interior tissues obliquely shaded.; the 
chalazal cushion cross-hatched ; the vascular strands are left white ; the cupule and stalk are dotted. 
р. c ., pollen-chamber; o.p.c., orifice of pollen -chamber ; c.c., central cone; s., sinus; cp ., canopy; 
с. , cupule; v.b., vascular strands. 
only a single imperfect specimen at his disposal, and further detailed study 
has served only to strengthen the bonds of resemblance. 
The points of agreement between Physostoma on the one hand, and 
the Lagenostoma-gxow^ (which includes Z. Lomaxii , Z. ovoides , and 
Conostoma oblongum) on the other, are as follows : — 
1 . All the seeds are of that type in which the apex of the nucellus 
alone is free from the integument. 
2. In all cases the free apex is transformed into a crevice- like pollen- 
chamber through the separation of the epidermis from the subjacent tissue 
of the nucellus. The orifice of the pollen-chamber is apical in position, 
and is borne at the extremity of a tube of varying length. 
