i 9 i6] ROE—COXCEPTACLE IX FUCUS 243 



modern trend is for simplicity rather than complexity, and since 

 the hairpit is simply an early stage of the conceptacle, the writer 

 is strongly inclined to reject both Bower's and Barton's terms 

 and retain the simpler term "hairpit," an exact translation of the 

 early German use of "Fasergriibchen." Bower's "central 

 column" is explained by examination of figs. 13-15. The old walls 

 become mucilaginous and sometimes several layers of mucilage 

 are seen between the meristematic portion and the ''column." 



Conclusion 

 There seems a clear line of advance from forms with continuous 

 patches of hairs and reproductive organs, as Nereocystis and allied 

 forms, to distinct sori, where the hairpit is the center of a repro- 

 ductive group, as in some Ectocarpaceae, Laminariaceae, Cutler- 

 iaceae, and Dictyotaceae, to distinct conceptacles scattered over 

 the entire vegetative body, as Splaclinidiuin, Hormosira, etc., to 

 a final distinct grouping at the apex of a shoot, as in Fucus, Pel- 

 vetia, and other Fucaceae, or on special side branches, as in Sar- 

 gassum, Turbinaria, etc. Similar lines of advance are already 

 commonly accepted for bryophytes and pteridophytes, in the one 

 restricted to arrangement of sex organs, in the other to arrangement 

 of sporangia. A striking parallel to Fucus is seen in Corsinia, Riccia, 

 and allied forms, where, step for step, the development of the dorsal 

 groove and subsequent appearance of sex organs (and even hairs) 

 from the basal portion repeats the history of the development of the 

 conceptacle of Fucus from an original segmentation of the apical 

 cell. In this one sees a forceful illustration that plants again and 

 again duplicate behavior in given conditions, even though in one 

 case the plant may be a gametophyte and in the other a sporophyte. 



Summary 



1. The conceptacle originates as a slightly modified contin- 

 uation of the external layer of the thallus, being segments of the 

 apical cell whose basal portions are constantly meristematic and 

 never entirely breaking down. 



2. The hairpit is a juvenile stage of the conceptacle, the sex 

 organs appearing in the same cavity as the mature hairs, but after 

 their loss. 



