1\ 



HOW TO KNOW THE SEAWEEDS 



48b Older parts of axes with a thick cortex; ultimate branches usually 



of similar length, at least more or less determinate. Fig. 78 ... . 



Rhodomela 



Fig. 78. 



Small portions of two species of Rhodo- 

 mela to show the production of determin- 

 ate ultimate branchlets from the cyUndrical 

 axes. A. Rhodomela subfusca (Woodward) 

 C. Agardh, the most widespread of the 

 three New England species. The spring 

 form is illustrated in which the tufted ap- 

 pearance of the tips is prominent. This 

 ^ aspect may in part be lost later in the sea- 

 B f\^ son by the eroding away of some of these 

 small branchlets. B. Rhodomela larix (Tur- 

 ner) C. Agardh, the common Pacific Coast 

 species from central CaUfornia northward. 

 A young axis is represented in which the 

 ultimate branchlets are much less abund- 

 ant and congested than in older plants. 

 Both figures X 1.2. 



Figure 78 



49a Thalli creeping; indeterminate (compound) branchlets alternating 

 regularly with small series of determinate (simple) branches. Fig. 



79 Herposiphonia 



Fig. 79. Herposiphonia 

 tenella (C. Agardh) Am- 

 bronn 



Part of a creeping axis 

 showing attachment rhi- 

 zoids and the series of 

 three simple, erect, de- 

 terminate branches alter- 

 nating with single short, 

 compound indeterminate 

 branches, X 50. This is 

 the commonest of four 

 species of this genus oc- 

 curring from North Caro- 

 lina through Florida. Sev- 

 eral other species occur 

 along the Pacific Coast. 



Figure 79 



They are usually quite small plants but may be conspicuous as epi- 

 phytes or in low algal mats or turfs. 



66 



