HOW TO KNOW THE SEAWEEDS 



31a Major branching mostly 2-ranked; ultimate branchlets more or 

 less verticUlate. Fig. 51 Wrangelia 



Fig. 51. Wrangelia penicillata 

 C. Agardh 



A small upper part of a plant 

 to show the branching in two 

 ranks and the tufted and some- 

 what verticillate manner of pro- 

 duction of the ultimate branch- 

 lets, X 5. This is the largest 

 of three species found in Flori- 

 da. It may reach a size of 

 10-20 centimeters. 



Figure 51 



31b Major branching distichous or multifarious; no order of branching 

 verticillate. Fig. 52 Callithamnion (in part); also Seirospora 



Callithamnion is a rather large genus of quite delicate, often small 

 plants which may be either epiphytic or saxicolous and which may be 

 found along almost any part of our coasts. Some of them are com- 

 pletely without cortication and will be treated elsewhere in this key 

 (step 76b). Several other species are corticated only in lower parts, 

 while C. pikeanum is corticated almost to the apex. In all of them the 

 alternate arrangement of the uniseriate branchlets of the last orders 

 and the tetrahedrally divided sporangia are characteristic (See Fig. 

 108). 



There is one plant of another genus which has these characters 

 and which will key out here. This is the Atlantic coastal Seirospora 

 griitithsiana Harvey (Fig. 53) which, however, is readily recognized by 

 its seirospores which are produced abundantly during the summer 

 in addition to the usual tetraspores. 



51 



