_Gnetopsis_, while agreeing with _Conostoma_ in the more important features, is distinguished by the apical plumes, the very slight development of a tent-pole prolongation of the nucellar apex (fig. 494, E, _t_), the smaller number of vascular bundles, and by the presence of an enclosing cupule (fig. 506, E). In its slight departure from radial symmetry _Gnetopsis_ forms a transition between the Radiospermeae and the Platyspermeae. It is undoubtedly the seed of a Pteridosperm, but nothing is known as to the nature of the vegetative organs of the parent-plant. II. +Trigonocarpales.+ In this group are included radially symmetrical seeds for the most part belonging to members of the Medulloseae. The peripheral zone of the nucellus is supplied with vascular tissue and the nucellus is free within the integument except at the base; it is superior and not semi-inferior[846] as in recent Cycads and in Lagenostomales. The ovule of _Myrica Gale_, in which the nucellus stands free within the single integument, affords an interesting parallel to seeds of this class in contrast to the usual Angiospermous type with a laterally coalescent nucellus. In _Myrica Gale_[847] the vascular supply is confined to the integument. There is a comparatively broad pollen-chamber and in some types the lateral tissue of the nucellus is prolonged as a tube within the micropyle. The usually ribbed testa is differentiated into an outer flesh (sarcotesta), a sclerotesta, and probably in most cases an endotesta or inner flesh. The ribs of the sclerotesta are in the majority of genera in multiples of three and in position correspond to the outer ring of vascular bundles. The presence of lacunar tissue in the sarcotesta of several genera may be correlated with dispersal by water. The apical region of the integument is not lobed but extends as a longer or shorter micropylar tube above the summit of the nucellus. In the differentiation of the testa, the form of the pollen-chamber, and in some other features, the seeds of this group present a general agreement with those of recent Cycads. The microspores are multicellular and larger than those of the Lagenostomales: in _Stephanospermum akenioides_ they measure 160μ × 100μ[848] while in _Aetheotesta_[849] they reach 360μ × 290μ. Genera. _Trigonocarpus_; _Tripterospermum_; _Ptychotesta_; _Hexapterospermum_; _Polypterospermum_; _Pachytesta_; _Stephanospermum_; _Polylophospermum_; _Codonospermum_; _Aetheotesta_; _Eriotesta_; _Gaudrya_. =Trigonocarpus.= Brongniart.