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HOW TO KNOW THE SEAWEEDS 



28a Axes completely corticated, unlike the ultimate branchlets which 



are uniseriate except for cortical bands. Fig. 44 Spyridia 



Fig. 44. Spyridia tilamentosa 

 (Wulfen) Harvey 

 A small part of a completely 

 corticated axis and part of two 

 banded ultimate branchlets, X 

 80. This dehcately bushy httle 

 plant occurs widely along the 

 Atlantic coast and in southern- 

 most California. It is essential- 

 ly a tropical species which in- 

 habits protected, warm bays 

 and pools in the northern parts 

 of its range. Another species, 

 bearing spines on the upper 

 nodes, occurs in Florida (S. acu- 

 leata (Schimper) Kiitzing). 



28b Axes and branches all similar, banded. Fig. 45 



CeTamium (in part) 



'Ooooooo 



(poooo 



ill. 



Figure 44 



Figure 45 



Fig. 45. Ceramium avalonae Dawson 



A small part of a plant to show the cortical bands, the caliper-like 

 tips characteristic of several species, and one manner of production of 

 tetrasporangia. The very fine lateral hairs are also present on a num- 

 ber of species. C. avalonae occurs in southern California. 



The genus Ceramium is a large one containing many incomplete- 

 ly corticated as well as completely corticated species (See Figs. 43, 61). 

 The incompletely corticated ones are usually quite small species of 

 warm waters, while the heavily corticated ones are usually larger and 

 of more temperate distribution. Specific identifications in the genus 

 must be made through the use of the more comprehensive floristic 

 works. The writer has presented an illustrated analysis of the twenty- 

 nine species occurring on the Pacific Coast of North America in Far- 

 lowia, vol. 4, pp. 113-138. 



47 



