rgoy] LAND—EPHEDRA TRIFURCA 287 



i 



gymnosperms leads the writer to conclude that the prothallial tubes 

 of Tumboa are best regarded as partial septations among the free 

 nuclei of the micropylar end, and that the condition shown by Tumboa 

 is a necessary stage in the elimination of the archegonium and the 

 evolution of the embryo sac. Such an explanation is in keeping with 

 the tendencies of every gymnosperm group. Of the male nuclei of 

 Tumboa we know nothing. 



In Gnetiim Gnemon, according to Lotsy/^ the female gametophyte 

 has the antipodal region compact, with all traces of walls lost in the 

 micropylar end, and the free nuclei all functional eggs. This is an 

 advance over the partially septate condition of Tumboa. Two male 

 nuclei are produced, but Lotsy is silent concerning their equality; 

 from the condition under which they function there can be little 



doubt that they are equal. 



Rumph 



Lotsy found slight traces of septation. In the species of Gnctum 

 investigated by Karsten'^ all trace of septation of the embryo sac is 

 absent at the time of fertilization. 



If we arrange a representative series of gymnosperms based on the 

 female gametophyte alone, the series will be as follows: Podocarpus 

 with its long-necked scattered archegonia; Torreya with usually a 

 single archegonium appearing almost immediately after the free nuclear 

 stage and having the antipodal and micropylar regions only slightly 

 differentiated; Ephedra irijurca with from one to three long-necked 

 archegonia with jacket cells sometimes simulating eggs, with antipodal 

 and micropylar regions sharply differentiated, the former compact, 

 the latter feebly walled; Microcycas with a loosely organized game- 

 tophyte at time of fertilization and having archegonia in clusters and 

 also clusters of multinucleate archegonia which in the opinion of the 

 writer, based on a comparative study of gymnosperms, are partial 

 septations among free nuclei; Tumboa with free nuclei functioning 

 as eggs in the partially septate micropylar end of the gametophyte; 

 Gnetum Gnemon with the antipodal region compact and the micropy- 



is Lotsy, J. P., Contribution to the life-history of the genus Gnetum. Ann. 

 Jard. Bot. Buitenzorg 11. 1:46-114. pis. 2-1 1, 1899. 



^^ Karsxen, H., Beitrage zur Entwickelungsgeschichte einiger Gnetum- Arten. 

 Bot. Zeit. 50:205-215, 221-231, 237-246. /?/5. 5, (5. 1892; also Zur Entwickelungs- 

 geschichte der Gattung Gnetum. Cdhn's Beitr. Biol. Pfl. 6:337-382. ph. 8-11 

 1893. 



