Howe: Phycological studies 585 



x6. The branch at the right represents a later stage in the development of the 



cortex, X 55- 



lown in 



17. Cross-section of stipe, X4- 



iS, Cortical region of stipe in cross-section, X I50- Drawn from a microtome 

 section 20 // in thickness. 



19. A stage in the differentiation of the cortical filaments later than that si 

 figure 16, X 55- 



20. P'inal form of cortical filaments of capitulum, X ^So. 



Figures 11-20 are drawn from formalin-preserved material of the type, no. 40jg 

 (Georgetown, Great Exuma, Bahamas). 



Plate 27. Sarcomenia JUamentosa 



Photograph of dried specimen i^no. 2844^ type — , Cape Florida, 29 Mr 1904, M. 

 A. H. ) attached to Sargasstt7fi^ natural size. 



Plate 2Z. Dttdresnaya n'assa 

 Photograph of dried specimen {jio. j/j, type — , Castle Harbor, Bermuda, 6 JI 



1900, M. A. H.), natural size. 



Plate 29 



I-l I . Sanomenia Jilamentosa 



1. Apex, of polyslphonous branchlet, ventral view, showing apical cell and origin 

 of the paired marginal cells and of the monosiphonous filaments, X ^93- 



2. Older part of branchlet, dorsal view, X ^93- 



3 and 4. Cross sections of uncorticated branchlets, ventral side downward, X ^93^ 

 5- Apical portion of uncorticated branchlet, with the unifarious monosiphonous 

 filaments, X4^- 



6. Branchlet viewed from margin, showing bases of the monosiphonous filaments, 



X 193- 



7« Part of an older branch, ventral view% showing origin of polysiphonous branch- 

 let (really from axial siphon), X 44- Marginal cells ai somewhat regular intervals are 

 enlarged and protuberant (potentially rhizoids). The monosiphonous filaments have 

 here disappeared, but the cell cut off from the anterior end of the ventral siphon mnrl<s 

 their former position in each thalkis-segment. Small intercalary cells, originating 

 chiefly from the pericentral siphons, constitute the beginning of the cortex. 



8. A similar branch, dorsal view, X44* '^^^ rhizoids are here growing o\xi, 



9. Surface view near the base of one of the largest stems seen, showing cortical 

 cells, X 40. 



10. Cross-section of a similar main stem X 44* 



11. Cross-section of an ordinary main axis in the basal third of the plant, X 44- • 

 Figures 9 and 10 are drawn from our no. 2S60 ; figures 1-9, and II are from the 



type material, no. 2844 (Cape Florida), 



12-26. Dudresnaya crassa 



12. Outer portion of peripheral filament. 



^Z~^S' Carpogonial branches. 



16 and 17. Auxiliary-cell branches; auxiliary-cell occupying middle of enlarged 



portion, lying between two much larger cells. 



