196 



EDGAR NELSON TRANSEATJ 



Where the waves have eroded headlands, among the detritus 

 that accumulates on the submerged beach are glacial boulders of 

 sufficient size to resist further movement. These are efficient 

 agents in the reduction of the force of the waves, the few large ones 

 protecting those of smaller size, all affording an extensive foothold 

 for the growth of the larger algae. At Lighthouse Point, Eatons 

 Neck, which may be taken as a typical example of this habitat, 

 a further barrier to erosion has been constructed by the mussels. 

 By means of their holdfasts they have formed a rather rigidly 

 cemented layer of shells often several inches in thickness over the 

 entire surface intervening between the rocks. 



Although I have named this formation for the Laminarias, 

 these plants do not extend so far west in the Sound as Cold Spring 

 Harbor. The dominant plant is Chondrus crispus. I have ob- 

 served farther north along the coasts of Massachusetts and Nova 

 Scotia that the Chondrus is one of the conspicuous plants of the 

 upper Laminarian belt. It seems therefore that we may best 

 classify these plants of the submerged beach as the Chondrus 

 Association of the. Laminaria Formation. The other members 

 of this association are Chorda jilum, Chordaria flagelliformis, Calli- 

 thamnion baileyi, C. americanum, Dictyosiphon foeniculaceous, 

 Cystoclonium purpurascens, Rhabdonia tenera, Ahnfeldtia plicata, 

 Griffithsia hornetiana, and principally on the mussels Polysiphonia 

 violacea. IVIany of these plants grow as epiphytes, the smaller 

 on the larger. The conditions which determine the habitat posi- 

 tion of these plants are largely unknown. Their rather constant 

 position and behavior when transferred to aquaria suggest an 

 adjustment to certain light intensities, to well aerated and sedi- 

 ment free water, to temperatures lower than those occurring in the 

 shallowest waters along shore. Unlike the forms of the next for- 

 mation the majorit}^ of th.es6 plants are of exceedingly delicate 

 texture, and exposure to the air for even a few minutes is harmful. 



This association is found at several points on the north side of 

 Lloyds Neck, with varying proportions of the component algae. At 

 Rocky Point, Center Island, somewhat the same conditions occur 

 on a smaller scale. The vegetation of the boulders off shore is 

 largely made up of migrants from the next association. In gen- 

 eral it may be said that the variety of algae in this association is 



