108 THE AMERICAN NATURALIST [Vol. XLIH 



gametophyte is so very different from anything present in the 

 lower achegoniates that relationships between the two groups 

 seem hardly possible. The work of Yamanouchi on Polysi- 

 phonia clearly indicates that the tetraspore mother cell when 

 present is the seat of reduction mitoses terminating the sporo- 

 phytic phase of the typical life history of the higher red algae. 

 The sexual organs of the red alga' are also far removed in struc- 

 ture from the sexual organs of the achegoniates. 



Davis in 1903 first pointed out the resemblance of the achegon- 

 ium and antheridium of the bryophytes to the plurilocular 

 sporangium or gametangium of the brown alga?, and advanced 

 the view that the former arose from such a type of sexual organ 

 as the latter through the differentiation of a sterile protective 

 envelope around the gametes (in response to terrestrial life 

 habits), and such sexual evolution as would give the highly de- 

 veloped condition of heterogamy present in the archegoniates. 

 Davis, however, was unwilling to concede the probability of an 

 origin of the archegoniates from the brown alga? because of the 

 ureal morphological differences between the two groups, but 

 suggested that there may have been forms of green alga? with 

 plurilocular sporangia, now extinct, from which the bryophytes 



Seh,. nek accepts the view of Davis that the sexual organs of 

 the archegoniates are homologous with plurilocular gametangia 

 and derived from them, but argues for a direct origin of the 

 archegoniates from the brown alga?. He gives an excellent 

 series of figures, selected from various authors, which illustrates 

 the principal forms of plurilocular sporangia and gametangia 

 }f the brown alga 1 , and presents a similar series of figures of 

 antheridia and archegonia of bryophytes and pteridophytes 

 showing various points of resemblance in their structure and de- 

 velopment. The resemblances are easily followed between the 

 gametangia of the lower brown alga? (Pha?osporea?) and the 

 sexual organs of mosses and most liverworts. However, there 

 are difficulties when the antheridia and oogonia of Dictyota, the 

 endogenous antheridia and sunken archegonia of Anthoceros, 

 and the sunken sexual organs of certain eusporangiate pterid- 

 ophytes, Lyeopod'mni. Selaginella, Isoetes, etc., are compared 



derive in a direct manner the former fronfthe latter. The re- 



