22 BOTANICAL GAZETTE [JANUARY 
is evolved de novo and is an organ sui generis.” But suppose we 
do assume that primitive angiosperms possessed a perianth, the 
origin of the perianth still remains to be explained. Even if we 
say that it is a direct derivative from a Bennettitean ancestor, 
its phylogenetic origin still remains a mystery. So if a perianth 
developed in some manner or other among the Bennettitales, 
might not the same thing have occurred among angiosperms, even 
long after they became a distinct group of plants? 
The question whether primitive angiospermous flowers were 
monosporangiate or amphisporangiate presents even greater 
difficulties than that concerning the primitiveness of the perianth. 
If angiosperms have descended from gymnosperms we would 
rather expect primitive flowers to be monosporangiate. Evidence 
from gymnosperms that amphisporangiate flowers are primitive 
rests almost entirely on a single, extinct, much specialized group 
of plants, the Bennettitales. This group no doubt represents, as 
CouLTER (7) suggests, ‘‘the end of a gymnosperm phylum.” More- 
over, that the proanthostrobilus of the Bennettitales corresponds 
closely to such a flower as that of Magnolia or Liriodendron s 
remains undecided. The resemblance is remarkable, yet if the 
view (17) that the Bennettitean inflorescence is a compound struc- 
ture is correct, and if the flower of Magnolia is not compound, then 
the resemblance becomes only a superficial one. 
If then we go back far enough in the evolution of angiosperms, 
the probability seems strong that the group was monosporangiate. 
Amphisporangiate flowers are unknown below angiosperms except 
in the Bennettitales and possibly Welwitschia. Although in a 
number of respects angiosperms and Gnetales have developed 
along parallel lines, it is now generally believed that the Gnetales 
are not transition forms leading to angiosperms. This view, 
however, does not preclude the possibility of common ancestry in 
the distant past. The Gnetales likely represent the end of a | 
gymnospermous phylum just as the Bennettitales do. So neither — 
group represents the direct progenitors of angiosperms. 
CovuLTER and CHAMBERLAIN (7) say: “It is ocmaed that F 
in the evolution of strobili among gymnosperms there were prob- 
ably two distinct tendencies: a monosporangiate strobilus (Cyca- 
