THE EVOLUTION OF PLANTS 
607 
features that characterize the Cycadofilicales, their 
development of a bisporangiate strobilus with two set 
of sporophylls, related to one an- 
other as they are in the flower of 
the Angiosperms. indicates a gen- 
etic relationship to that group, as 
does also the fact that the seeds, 
enclosed in a fruit, possess a dicot- 
yledonous embryo, without endo- 
sperm. In other features the Ben- 
nettitales are unlike the Angio- 
sperms; the ovules, for example, 
are enclosed by sterile scales, in- 
stead of by the carpels on which 
they are borne, and the protrusion- 
of the pollen-chamber through the 
micropyle signifies the gymno- 
spermous type of fertilization. 
These and other comparisons in- 
dicate that the Bennettitales were 
essentially Gymnosperms having 
certain Angiospermpus characters, 
and therefore, while they are not 
to be considered as the ancestors 
of the Angiosperms, it is probable 
that they and the modern dicoty- 
ledons are both descended from a 
common branch of the ancestral 
tree. 
flower of the magnolias most 
closely resembles that of Cycadeoidea in the spiral arrange- 
ment of its stamens and pistils (Figs. 428 and 429.) . How 
FIG. 429. Magnolia. 
Flower with perianth re- 
moved, showing the com- 
pound pistil, and four of the 
stamens. Most of the sta- 
mens have been removed. 
Note their spiral arrange- 
ment as shown by the scars 
Among modern plants, the at the points of attachment. 
(Cf. Fig. 428.) 
