238 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



EXPLANATION OF PLATE XXL 



Figs. 15-1S, and 20-22, drawn with Abbe's camera lucida, obj. Leilz |, 



ocular No. 3. 

 Fig. 19 drawn with Abba's camera lucida, obj. Leitz |, ocular No. 3. 



Porphyra occidentalis. 



Fig. 15a. Surface view of vegetative part of frond. 



Fig. 15^. Cross-section of vegetative part of frond. 



Fig. 16. Cross-section of antheridial part of frond, showing stages in the 



development of the antheridia. 

 Fig. 17a. Surface view of antheridial part of frond. 

 Fig. I'jb. Cross-section of antheridial part of frond. 



Porphyra variegata. 

 Fig. iS. Cross-section of vegetative and sporocarpic part of frond. 



Porphyra naiadum. 



Fig. 19. Cross-section of blade of Zostera and of base of frond of P. 



naiadum. 



Fig. 20a. Surface view of vegetative part of frond. 



Fig. 20b. Cross-section of vegetative part of frond. 



Fig. 2ia. Surface view of sporocarpic part of frond. 



Fig. 216. Cross-section of sporocarpic part of frond. 



Fig. 22. Cross-section of young frond with base. 



