Page 5 - Bulletin of the Cupressuss Conservation Project vol04_nr1 2015

A typical microsporangiophore consists of a central stalk about 1 mm long, 2 abaxial sporangia
each about 0.4-0.5 mm in diameter and an adaxial green more or less triangular, slightly serrate,
upright scutellum 0.5-0.7 mm long and 0.8-1 mm wide (fig. 3A, 3B, 3C). The ripe sporangia are
parallel to the central stalk of the microsporangiophore (fig. 3A). The scutellum of the most distal
microsporangiophores is strongly elongated, and about 1.1-1.8 mm long and 0.8-1 mm wide
(figs 3D, E). Especially in the scutellum of the most distal sporangiophores a huge resin duct is
developed (fig. 4E). The microsporangia and the scutellum are strongly fused with each other
(figs 3C, 3E). The scutellum is attached in an angle of nearly 80° to the stalk and also fused with the
sporangia (fig. 3C). In young cones, the scutellum of the microsporangiophores are covering the
sporangia of the more distal microsporangiophores. Before anthesis nearly only the phylloid part is
visible externally. The cone-axis elongates strongly at anthesis and the microsporangia are freely
exposed to the airflow. Within the sporangiophore no intercellular spaces are developed (figs 3C,
3E).

For better pollen release microsporangiophores diverge distally from each other at anthesis. At
pollination time each microsporangium opens along a median, longitudinal preformed line
(fig. 3A left) and releases the pollen grains over a period of 7-13 days. The release of the pollen
starts even when the cone is not already completely open. The majority of pollen grains are
collected first on the upper surface of the lower microsporangiophores especially on the scutellum.
From here the pollen is taken secondary by the airflow, when the cone-axis has reached its final
length. After releasing the pollen the cones dry out and are abscised as a unit.

The majority of cones are unbranched. Only some pollen cones are branched structures, showing
1-2 lateral axillary units in the basal part (fig. 2B). Each of these lateral units is inserted in the axil
of a green triangular bud scale of the terminal cone. The lateral units are originated from a separate
bud (figs 1E, 1F). Thus also at the base of the lateral cones persisting bud scales develop (figs 2E,
2F). In the investigated cones only the most basal bud scales were fertile – the distal ones were
always sterile. The vascular bundle strand of the lateral cone and the fertile bud scale enter the
vascular bundle strand of the axis of the terminal cone in separate strands (fig. 2F). They do not
fuse. In the anomalous branched pollen cones the development of the terminal pollen cone is
hurrying ahead to the lateral cones.

3.2 Morphology of pollen

The pollen grains are bisaccate (figs 5A, 5B, 5C). Their overall length including the sacci varies
between 40-50 µm. The corpus is elliptic and varies between 27-36 µm x 20-26 µm (fig. 5C). The
sacci are broadly attached at the corpus (figs 5A, 5B). They are between 15-20 µm in diameter and
between 10-12 µm in height. The two sacci are attached at an obtuse angle to the corpus, ranging
between 110°-130° (fig. 5A). The outer surface of the sacci is covered with several tiny papillae and
has several perforations (figs 5A, 5B, 5E). The corpus has a strongly rugulate, thick sculpturing
without perforations (figs 5C, 5D). The leptoma is 18-24 µm long and 8-13 µm wide. Its surface is
fossulate. Perforations are absent (figs 5B, 5F).

4 Discussions

In its vegetative parts Podocarpus gnidioides differs significantly from the other taxa of the
subclade Australis especially in some morpho-anatomical characters of the leaf, e.g. by forming a
double layered hypodermis and lacking of hypodermal fibres between the abaxial stomata rows
(KNOPF et al. 2011). When regarding the morpho-anatomical data of the pollen cones Podocarpus
gnidioides complies with those of the other taxa of subclade Australis. Despite the relative isolated
systematic position of Podocarpus gnidioides among the other New Caledonian Podocarpus
species, its pollen cones do not have special features that are exclusively presented in this taxon.
They show all features typical for pollen cones among Podocarpus.

─ 38 ─ Bulletin CCP, vol. 4, n° 1.