375 
3". Bands very narrow, usually c. 50 #, rarely over 100 « high, con- 
sisting of 1—3 (usually 2) transversal rows of cells; cells in the 
lower edge of the bands often with parallel upper and lower sides; 
frond sometimes creeping........................ ENTER ft. C. eimbrieum. 
1*. Cortication partly or entirely continuous. 
2. Cortication with distinct bands in the upper part or in a greater 
part of the frond. 
3. The outer cortical cells very small, 7—10 « in diameter, usually 
loneitudinallyzeloneated ers ee 12. C. Boergesenii. 
3*. Not so. 
4. Bands with sharply limited lower border occur; bands at least 
thrice higher than the diameter. 
5. Ramification biseriate alternate or dichotomous; in the 
latter case the apices are incurved ..................... 16. C. fruliculosum. 
5*. Branches not biseriate, apices straight, at least in older 
specimens. 
6. Bands often over 2 mm high, usually distinct below, 
though often approaching each other .............. 17. €. seplentrionale. 
6*. Bands not 10 high. Cortication usually continuous 
below. Zapicesithinun.n a EE TARA te a 15. C. Areschougii. 
4*. Bands with sharply limited lower border do not occur; bands 
not so high, increasing downwards in various degree. 
5. Cells of the bands, in particular of the upper ones, are 
arranged in distinct longitudinal rows; distinct bands only 
in the upper parts of the frond ...................... 13. C. scandinavicum. 
5*. Cells not in distinct longitudinal rows; distinct bands in 
the upper parts or in greater parts of the frond. 
6. Bands slightly increasing downwards, cells in the lower 
border often broad Au... u. ek era ele cet co 14. C. abyssale. 
6*. Bands much increasing downwards; altogether slight 
difference between upper and lower border of the band. 
7. Cortication usually continuous over more than two 
thirds of the length. 
8. Apices very thin, often capillary, much branched. 
9. Main axes much developed, with secondary 
branches ray. cece acura a REE ne og naan ae 9. C. arborescens. 
9*. Ramification usually pronouncedly dichotom- 
ous, secondary branches not much developed. 8. C. rubriforme. 
8*. Apices vigorous, slightly branched near the top. 
9. Colour dark, often much developed main 
stems and secondary branches; cortication 
continuous over the greater part of the frond 11. C. atlanticum. 
9=. Colour light; vigorous main stems without 
secondary branches.......... SE Sie ob 10. C. Rosenvingii. 
7*. Bands distinct in the upper third of the frond; 
SA COL OUT ER ee er 7. C. danicum. 
2*. Cortication continuous over the whole frond ......... DEE RSR ET SU TU DURE 
48° 
