232 
MORPHOLOGY 
FIGS. 525, 526. Gnelum latifolium: 525, branches 
bearing ovulate strobili ; 526, part of ovulate strobilus. 
After BLUME. 
of swimming sperms. In Ephedra 
a remarkable funnel-shaped pollen 
chamber is developed by the break- 
ing down of the nucellar tissue (fig. 
528), which extends to the embryo 
sac and exposes the necks of the 
archegonia; hence in pollination 
the pollen grains may come to rest 
in contact with the archegonium 
necks. In Gnelum the tip of the 
nucellus is more or less disorgan- 
ized, and this is the only trace of 
a pollen chamber (fig. 530); while 
in Tumboa there is not even a 
trace. 
Female gametophyte. The struc- 
ture of the female gametophyte in 
Gnetales is of great interest, for 
there is an evident approach to- 
wards the angiosperm condition. 
Ovule. The ovule has 
two integuments, the inner 
one forming a long tubular 
micropyle, which is a 
marked feature of the 
group (figs. 521, 528, 530). 
The nucellus has the usual 
gymnosperm feature of a 
heavy mass of sterile tissue 
overlying the megaspore 
mother cell (and later the 
embryo sac). In all the 
preceding groups of gymno- 
sperms, except Coniferales, 
this overlying tissue is 
beaked and contains a 
pollen chamber, a structure 
associated with the presence 
FIG. 527. Ovulate strobili of Gnetum, 
with fleshy seeds maturing. 
