BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 



541 



Pyramid RocK 



Chart 271. — Distribution of algse on Spindle Rocks, July 22, 1905. 



The only conspicuous green alga was Ulva Lacluca var. rigida (5), now full grown and forming large 

 patches on some of the rocks. There was a very well-defined brown zone just below low-water mark 

 (the dotted line) composed of Chordaria flagelliformis (28) and old Scytosiphon lomcntarius (26). Ecto- 

 carpus confervoides {14) was plentiful on the Chordaria and Scytosiphon. Phyllitis fascia had disappeared. 

 Nemalion mullifidum (40) fringed most of the rocks at low- water mark, and below was a characteristic red 

 zone of Polysiphonia violacea (48) and Ceramium rubrum (43) mixed with the Chordaria, and with Chon- 

 drus crispiis (49) abundant from 1-5 feet below low water. 



Listofalg£e: Calothrix scopulorum, i, small patches on barnacles and rocks; Rivutaria alra, 2, on 

 barnacles; Ulolhrix implexa, 3, on Pyramid Rock; Uha Lactuca var. rigida, 5, abundant on tops of 

 rocks; Enteromorpha intestinalis, 7, few patches; Cladophora gracilis, g, iew tu!ts; Codiolum gregarixim, 

 12, on barnacles; Ectocarpus confenoides, 14, abtmdant on Chordaria and Scytosiphon; Scytosiphon 

 lomentarius, 26, much old growth ; Chordaria flagelliformis, 28, abundant; Mcsogloia divaricala, 29, few 

 patches; Chorda filum, 31, large patches; Laminaria Agardhii, 33, few groups; Fticus vesiculosus, 35, 

 few plants; Nemalion mullifidum. 40, abundant; Ceramium rubrum, 43, abundant; Chondria dasyphylla, 

 44, few plants; Polysiphonia violacea, 48, abundant; Chondrus crispus, 49, abundant. 



