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WALTER P. THOMPSON 
much as a true perianth. The objections to this view are as follows: 
(i) As previously shown the anatomy and development of the inner 
envelopes of other members of the Gnetales indicates that they are 
composed of two fused foliar members and that they are not integu- 
ments. (2) The outer envelope has not the functions of a carpel in 
collecting pollen and conducting pollen tubes. (3) The envelope of 
the staminate flower of Gnetum is obviously of the same type and 
certainly cannot be considered an ovary. The homology of these 
envelopes in male and female flowers is shown by their form, develop- 
ment and anatomy. (4) The similar envelope of the male flower of 
Welwitschia encloses the stamen cycle and therefore cannot be con- 
sidered an ovary. These objections seem to constitute too great a 
body of evidence for the view to be longer tenable, despite the evident 
similarity in form between the outer envelope and a true ovary. 
Finally there is the theory recently advanced by Lignier and 
Tison (17, 18) that the innermost envelope is a true ovary and that 
the two outer envelopes are in the nature of a perianth. This implies 
that the ovule is destitute of integuments. There appears to be much 
more evidence in favor of this view than any of the others partly 
because of the facts revealed in this article and partly because it ac- 
counts for the morphology of the similar envelopes of other Gnetalean 
flowers and indeed for their whole structure. It is clear that in any 
theory of the morphology of the envelopes in Gnetum, the structure 
of the female flower of Gnetum must be harmonized not only with 
that of the male flower but also with that of the flowers of the other 
genera of the Gnetales. The general argument as developed by 
Lignier and Tison, chiefly in connection with the flower of Welwitschia, 
will first be stated and then applied to Gnetum. 
It is admitted by practically all investigators that the structure 
of the male flower of Welwitschia with its abortive ovule above the 
cycle of stamens indicates that the immediate ancestors of the genus 
bore hermaphrodite flowers arranged on the Angiosperm plan, and 
that the female flower has resulted from the suppression of the stamen 
cycle. Owing to the similarity of the flowers of other members of the 
Gnetales to those of Welwitschia it is evident that they too are re- 
duced from a hermaphrodite condition. This conclusion is inde- 
pendently confirmed by the discovery (18) of abnormal flowers of 
Gnetum scandens bearing stamens within the second envelope. With 
this general arrangement in mind we may now consider the mor- 
phology of the individual parts. 
