PICTURED-KEY TO THE COMMON GENERA OF 

 MACROSCOPIC MARINE ALGAE OF THE 



UNITED STATES 



la Thallus consisting of a single large, subspherical cell with basal 

 attachment. Fig. 13 124 



Fig. 13. Valonia ventricosa J. Agardh 



An entire plant showing the single large 

 spherical cell with basal rhizoids for attach- 

 ment, X 1.5. 



Figure 1 3 



lb Thallus consisting of more than one cell, or if coenocytic, at least 

 not subspherical in form 2 



2a Thallus more or less calcareous, the calcium carbonate deposited 

 superficially in the outer tissues, in articulated segments, or through- 

 out the entire thallus 106 



(If in doubt about the calcareous nature apply a little dilute acid 

 to a clean piece of thallus and watch for bubbles under a dissect- 

 ing microscope.) 



2b Thallus not calcareous 3 



28 



