Affinities of the Palaeozoic Seeds of the Conostoma Group. 35 
presence, however, of a series of apical tufts at the micropyle is at least 
consistent with a lobed antecedent, and this equally whether these tufts 
consist of hairy prolongations of the actual ribs of the seed or whether, 
on the other hand, they are merely the expression of localized proliferations 
of the trichomes which may, however, have corresponded in position. In 
order to give precision to the remarks on Gnetopsis and to facilitate com- 
parison with the other types, we have embodied our view of the structure of 
this seed in the convenient form of a text-figure (p. 34). The necessity for a 
detailed reconstruction happily does not arise, as we understand there is some 
prospect of Gnetopsis undergoing re-investigation at the hands of our friend 
Professor C. E. Bertrand, to whose good offices we are deeply beholden for 
the opportunity of consulting the specimens on the present occasion. 
2. Comparison with Physostoma . 
This seed belongs to an interesting generalized type in view of the 
prominence of the ribbing and the lobing of the testa. Moreover, the 
presence over the surface of the seed of large hairs probably containing 
mucilage affords a further variant of the mechanism which is illustrated 
by the 1 blow-off’ of Conostoma and the mucilage pegs of Lagenostoma. 
The lagenostome of Physostoma with its all but sessile mouth forms 
a connecting link between those of Lagenostoma and Conostoma ; the former 
with its tubular prolongation reaching to the surface of the seed, the latter 
with a true micropylar tube, integumental in origin, which fitted to the rim 
of the cup-like lagenostome with marvellous nicety. 
Within the seed the ‘ tent-pole 1 prolongation of the megaspore chamber 
projected into the floor of the lagenostome, thus outstripping all other known 
cases. On the other hand the plinth is practically undeveloped. These 
facts of structure taken in connexion with the large number of ribs and lobes 
appear to be consistent with the view that Physostoma preserves several of 
the more archaic traits of the unknown precursors from which the various 
types may be supposed to have sprung. Among the features which on this 
view would belong to these precursors must be included the lobed, unfused 
micropyle, the many ribs, the mucilage epidermis, the terminal, indurated, 
capacious lagenostome, and the ‘ tent-pole \ The extension of the plinth, on 
the other hand, is to be regarded as a later intercalation. 
3. Comparison with Lagenostoma. 
The features which unite Lagenostoma and Physostoma are too well 
known to need recapitulation here. 1 As compared with Conostoma the 
loculi of the canopy in Lagenostoma had a more extensive filling tissue and 
relatively thinner peripheral and radial layers of sclerized elements, the 
1 Oliver : On Physostoma. Ann. of Bot., vol. xxiii, p. 108. 
