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most primitive form known and can directly be compared with 

 the Gymnosperms. Inside of the macrospore a prothallium ') 

 is formed in which Archegonia very much like those of the 

 Gymnosperms arise. 



In the Genus Welwitschia a definite prothallium is formed 

 also , but the Archegonia are very much reduced consisting of 

 nothing but an prothalliumcell whose wall grows out to a 

 projection for the purpose of meeting the pollentube. 



In the Gneta described by Karsten no prothallium is formed 

 before fertilisation and some of the free nuclei are fertilised. 

 The formation of the prothallium here is but retarded; it 

 takes place after fertilisation has occurred. I therefore can agree 

 perfectl}^ with Karsten in considering his Gneta as showing a 

 case like Welwitschia , where the cells of the prothallia have 

 not been formed. In other words Karsten's Gneta can be com- 

 pared to a Welwitschia being fertilised at an earley stage of 

 its development. 



How about Gnetum Gnemon? 



The upper part of the embryosac of Gn. Gnemon behaves 

 like the lohole of the embryosac of the Gneta described by 

 Karsten and consequently could perfectly well be compared 

 with the whole of the embryosac of Welwitschia; the lower 

 part of the embryosac of Gn. Gnemon fills with a doubtless 

 prothallium in which even organs, ressembling rudimentary 

 Archegonia are found. This very peculiar behaviour, the for- 

 mation before fertilisation of a Welwitschia prothallium reduced 

 to its bare necessities viz. the nuclei only in the upper part 

 and of an Ephedra- or Welwitschia-like prothallium in the lower 

 part made me think of the possibility of considering the em- 

 bryosac of Gnetum as the homologon of two macrospores. The 



1) If we compare the different ways in which prothallia and » endosperms" arise 

 (as illustrated by the investigations of Jaccard for Ephedra, Pfeffer and Heinsen 

 for SelaginoUa, Campell for the Hydropteridae miss Soleska for the Gymnosperms, 

 and many others for the groups allready mentioned and for the Angiosperms , we 

 must conclude, I think, that it is almost hopeless to suppose that they will ever 

 show us what is primitive and what is due to secundary adoptations. 



