In many conifers, but by no means all, the ovule is borne not directly in the axil of the cone scale (bract), as it should if it were a simple structure, analogous to a flower, but on a secondary axis, the ovuliferous scale, itself directly in the axil of the bract scale, as if the cone were analogous to an inflorescence.
Within several groups of conifers a reduction series can be demonstrated in which the ovuliferous scale, assumed to be present ancestrally, has disappeared.
3m, n), each subtending an ovuliferous scale consistently bearing two adaxially placed ovules, their micropyles directed toward the cone axis.
These include at least five morphotypes of Glossopteris leaves and the glossopterid ovuliferous
organs Lidgettonia africana, Rigbya arberioides and Plumsteadia gibbosa, and the glossopterid polleniferous organ Eretmonia natalensis.
Pistillate flowers solitary on long slender pedicels 6-15 mm long, glabrous; ovary ovoid, acuminate, smooth or with very few (2-3) spines, basal ovuliferous
zone of 1.5 mm long, acumen of 1 mm long, 4-ovulate; hypanthium 2 mm diam., petals 1.25 mm x 1.5 mm, the stigma globose, sessile.
However, Peltaspermum has been redefined by Poort and Kerp (1990) as a natural genus including sterile foliage and ovuliferous
organs for the species P.
Proof of this are the petrified pine cones found with their ovuliferous
scales, still unopened, a development that requires only seventy-two hours.
8), the axis of the short shoot had become rudimentary and bore five distal sterile scales and two or three basal stalk-like megasporophylls, the whole, with the subtending bract, corresponding to the bract and ovuliferous
scale of a modern pine cone.
There is no evidence of ovuliferous scales subtended by bracts.
Conifers with an evident ovuliferous scale could be derived from the Lebachia type and the Cephalotaxaceae from the Ernestiodendron type.
Controversy has centered on the nature of the megasporangial enclosure or ovular integument and the interpretation of the ovuliferous scale.
In these the fleshy structure comprises part or all of the ovuliferous scale, sometimes fused with the subtending fertile bract.