PLATE 12 



Ulva Lima L. 



Fig. 1, A vertical section through the margin of a frond showing the separa- 

 tion of the two layers. Plant from Friday Harbor, Washington. X 250. 



Fig. 2. A surface view of fig. 1. X 250. 



Fig. 3. The same view as fig. 1. Plant from Admiralty Island, Alaska. 

 X 250. 



Fig. 4. A surface view of fig. 3. 



Gayella constrieta S. and G. 



Fig. 5. Habit sketch of a whole plant. X 30. 



Fig. 6-8. ShoAving the development of rhizoids. 



Fig. 9. Two enlarged segments showing shapes and arrangement of the cells 

 in surface view. X 100. 



Fig. 10. A cross section of a large segment showing the radial arrangement 

 of the cells. 



Figures 5-10 are from Gardner, New Pac. Coast Mar. Alg. I, 1917, pp. 377- 

 416, pi. 33. 



[332] 



