90 



In this way the only difference between the female flowers 

 of Gnetum and those of Ephedra, if one accepts Jaccard's and 

 my views, consists in the fact that Ephedra has one perianth- 

 whirl while Gnetum has two. In both flowers the ovule pro- 

 vided with but one integument has arisen by direct transfor- 

 mation of the top of the axis of a bud. In the incomplete 

 female flowers of Gnetum Gnemon the internal perianth whirl 

 disappears, they are consequently built in exactly the same 

 way as Ephedra-flowers. In these questions, of course, much 

 if not all, depends on personal appreciation of the observed 

 facts ; yet, the fact that I came to results corresponding closely 

 to those obtained by Jaccard in the case of Ephedra have 

 given me the satisfaction of being able to dismiss the subject 

 from my mind which is practically all one can obtain in a 

 case like this. 



ORIGIN OF THE EMBRYOSACS. 



As I have no new facts to offer concerning this point I must 

 refer the reader to the historical part at the beginning and 

 the speculative part at the end of this essay. 



THE EMBRYOSACS AND THEIR CONSEQUENT DEVELOPMENT. 



a. External changes. 



If we examine a flower of Gnetum Gnemon L. at a stage 

 where the three envelops are allready well developped we ob- 

 tain a picture like fig. 18 PI. III. The larger and smaller cells 

 near the base of the nucellus are a number of embryosacs. 

 The embryosacs of this section are drawn at a much more 

 considerable enlargement in fig. 19 PI. III. The first fact which 

 is noted is the comparative thickness of the embryosac walls 

 which make them appear much more cryptogamous than the 

 embryosacs of most higher plants. In the section we have be- 

 fore us four embryosacs are seen lying in the same plane, 

 while a fifth is lying in a plane a little above the other ones. 



