i88 
MORPHOLOGY 
that the microsporangia have advanced very little beyond the fern 
level. 
Ovulate structures. The megasporangiate structures, however, 
have advanced very far beyond the fern level, and are very peculiar 
(fig. 431). The seeds terminate 
long and slender stalks, which are 
packed among interseminal scales 
that are also stalked structures. 
The stalked seeds and interseminal 
scales are arranged so as to form 
an ovoid, fmitlike body, with a 
mosaic surface composed of the 
flaring tops of the interseminal 
scales, wedged between which 
the micropylar tubes of the seeds 
protrude. If this structure be 
compared with the seed-bearing 
structures of the Cycadofilicales, 
especially those in which the seeds 
terminate the naked branches of 
a pinna, it will be observed that if 
these branches be reduced to a 
single axis, the condition in Ben- 
nettitales is obtained. The inter- 
seminal scales are probably sterile 
megasporophylls ; and all the 
megasporophylls, leaflike and 
spreading in Cycadofilicales, are 
compacted into a strobilus in 
Bennettitales. 
FIG. 429. Strobilus of a species of Seeds. The structure of the 
Cycadeoidea, in which the seeds are mature, seeds has been obtained from SCC- 
and showing the shoulder (a) which bore the t j whjch ghow & ^^ j 
stamens. After WIELAND. 
suggesting a rudiment of the in- 
vesting and husklike cupule of some of the Cycadofilicales; a two or 
three layered testa ; and a large dicotyledonous embryo completely 
filling the seed (fig. 432). This embryo is unlike that of any living 
gymnosperm, in that in developing it destroys all of the endosperm 
(see p. 202). 
a 
