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epidermis. Between this and the tissue, there is a cavity, 
which has undoubtedly been formed by the separation of 
the epidermis and the underlying tissue. This bell-shaped 
cavity is the pollen-chamber, in its lower part the pollen 
grains are found. 
In the nucellus lies a megaspore containing a prothal- 
lium. As in all pteridospermous seeds an embryo has 
never been found. 
$ 6. Sphaerostoma ovale Benson. 
Literature: Benson (16). 
Fiqure-16 p.23: 
Sphaerostoma ovale formerly described by Williamson 
as Conostoma ovale and intermedium, is likely the seed 
of Heterangium Grievii. 
The seed strongly resembles that of Lyginodendron 
Oldhamium, like the latter it is composed of an outer 
envelopment, the cupule (called by Miss Benson ‘the 
outer integument) and a central portion, formed by the 
nucellus and an integument, which are concrescent for 
the greater part. 
Without cupule the seed has a length of about 3,5 mM 
and a diameter of 2,2 mM. In transverse sections it seems 
to be round, except in the lower and upper part, where 
the form is more or less octagonal. 
Mostly the cupule is no longer preserved so that for 
the present a minute description cannot be given. The 
tissue is much more regular than that of the integument 
and contains several vascular bundles, structure and 
number of which were difficult to observe. It is possible 
that at the top, just as in Lagenostoma it consisted of 
lobes, but in most transverse sections it was seen as a 
closed ring. 
