BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 



543 



Chart 273. — Distribution of algae on Spindle Rocks, September 19, 1904. 



This chart is introduced to show variations that may be present in the algal life on the same rocks 

 at the same season but in different years. It should be compared with chart 272, plotted September 2, 

 1905. The charts agree in having Ulva Lactuca var. rigida (5) as the conspicuous green alga on the tops 

 of the rocks. There was no Chordaria flagelliformis this season and consequently no zone of brown 

 algae, although Scytosiphon lomentarius (26) grew in scattered patches. Nemalion multifidum (40) formed 

 a zone of thick growth above low-water mark (the dotted line) on rocks III, VII, VIII, and Pyramid 

 Rock. The most conspicuous zone was below low water and composed of Ceramium rubrum (43) and 

 Polysiphoniafibrillosa (46). The Polysiphonia fibrillosa, which was not present at all in 1905, this season 

 took the place of Chordaria flagelliformis and Polysiphonia violacea (48), usually abundant, but scattered 

 plants of the latter were present. Chondrus crispus, as usual, was abundant, extending into deeper 

 water below the Polysiphonia. 



List of species: Ulva Lactuca var. rigida, 5, abundant; Scytosiphon lomentarius, 26, patches on rocks; 

 Chorda filum, 31, large beds; Laminaria Agardhii, 33, scattered patches; Fucus vesiculosus , 35, scattered 

 plants, Sargassum Filipendula, 36, few plants; Nemalion multifidum, 40, abundant; Ceramium rubrum, 

 43, abundant; Polysiphonia fibrillosa, 46, very abundant, fringing rocks just below low-water; Polysi- 

 phonia violacea, 48, few; Chondrus crispus, 49, abundant. 



