GNETALES 371 



of cones involved in the young condition in rather large sheltering, 

 bracts. Immediately above the series of bracts microsporophylls 

 (usually of large size and pinnate structure) are attached to the 

 axis of the strobilus. The main part of the cone is, however, 

 made up of the seminal organs, consisting of pedicels to which 

 single seeds are attached in an orthotropous manner. The seeds 

 are somewhat sheltered by the swollen ends of sterile appendages 

 inserted among the seminal organs on the axis. The protected 

 condition of the seeds has given rise to the suggestion of angio- 

 spermous organization. This apparently cannot be regarded as 

 more than the merest analogy, since the seeds are not shel- 

 tered within a closed megasporophyll and the pollen is deposited 

 directly upon them after the typical gymnospermous manner. 

 Further, the cycadean fertilization is not even siphonogamous, 

 as would be expected of a group presenting valid claims to be 

 regarded as ancestral to the highest seed plants. Nor is the 

 analogy with the flower of the angiosperms to be given greater 

 weight, for the arrangement alone and not the intimate organiza- 

 tion of the reproductive parts shows any real resemblance to 

 the conditions found in the floral structures of the angiosperms. 

 An androgynous cone such as is frequently present in the Coniferales 

 supplies an equally good basis for comparison; for here the bracts 

 below correspond to the floral envelopes of the flower, while the 

 lower whorls of microsporophylls simulate the anthers, and a 

 plausible resemblance to the carpellary whorls is presented by the 

 ovuliferous scales of the upper region of the modified cone. The 

 most striking objection and the same as occurs in the case of the 

 Bennettitales is the fact that the ovuliferous scales are not angio- 

 spermous. The siphonogamic fertilization of the Araucarian coni- 

 fers, on the other hand, reveals a nearer degree of resemblance to 

 the conditions found in the flower of the angiosperms than does 

 the zoidogamy of the archigymnospermous Bennettitales. In the 

 present state of our ignorance of the fossil ancestors of the Angio- 

 spermae it seems impossible to fix on any group of gymnosperms, 

 living or extinct, except the Gnetales, which can be regarded with 

 any degree of probability as having been either ancestral to the 

 highest of the seed plants or even cognate with them. 



