Maritime Distriet: New England. 383 
3. Marine Algal- and Plankton Formation. 
The marine plants of the northeastern coast of North America naturally 
arrange themselves in several shelves‘), the Ulva shelf, the Fucus shelf, 
the Laminaria-Chondrus shelf and the Deep Sea shelf. 
Ulva Shelf. On this shelf Ua latissima is found in great abundance. 
Wherever pools of water are left by the tide, this plant occurs and I have 
found it plentifully on Conanicut Island growing in the pools formed in the 
exposed slate rock of the coast at that point. 
Four species of Enteromorpha are found on this shelf Enteromorpha intestinalis, E. compressa, 
E. clathrata, E. Hopkirkii. Along with these and firmly adhering to the rocks clumps of Clado- 
phora rupestris, C. uncialis, C. flexuosa are found, and also gelatinous masses of Hormotrichum 
Youngianum. Here is also a dwarf species of Fucus. It grows in the corners and crevices of 
water pools and may be a form of F. vesiculosus. 
Fucus Shelf. The first and uppermost plant is Fucus (Ascophyllum) nodosus 
ranging as far south, as New York Bay. It covers a belt of shore from one 
to three yards in breadth and is frequently covered by Ceramium rubrum. 
It grows below it and retains more water among its fronds than the previous 
more leathery plant. It is parasitized by Zlachistea fucicola and Ectocarpus 
siliquosus and completely covers the rocks upon which it grows. Fucus fur- 
catus occupies the chief place in what might be termed the third sub-shelf. 
It is found at the ordinary low water mark and is scarcely ever altogether 
out of the water. Under its folds Chondrus norwegicus? occurs adherent to 
the rocks with Gzgartina mamillosa. 
The pools at this me are the homes of Chondrus crispus, Halasaccion ramentaceum, 
Cystoclonium purpurascens together with Hypnea musciformis, Chordia flagelliformis, Rhodymenia 
palmata, Porphyra re Chaetomorpha melagonium, with Delesseria sinuosa in the deeper 
and more shady pools. 
Laminaria-Chondrus Shelf. The marine algae of this shelf are Agarum 
Turneri, Alaria esculenta, Laminaria digitata, saccharina, fascia, phyläitis, 
dermatodea, while at greater depths is found Chondrus crispus, which grows 
in great abundance south to Long Island. 
Deep Sea Shelf. The finer American marine algae occur in deep water. 
Laminaria longieruris eight to twelve feet long occurs here as far south as 
Cape Cod. The prevailing deep sea algae are Rhodymela subfusca, Delessaria 
sinuosa, alata, denticulata, Euthora cristata, Phyllophora membranifolia, (not 
common), Pizlota serrata and elegans, Punctaria tenuissima, Folysiphonia förillosa. 
The following is a list of the marine algae found on the shores of Peni- 
kese Island’). : 
ı) Kemp, Rev. ALex. F.: On the shore Zones and Limits of marine ae on the north- 
nn. coast of the United States. Canadian Naturalist and Geologist 1862: 20, 
) Jorpan, Pror. D. S.: The Flora of Penikese Island. American ae 1874 VIII 
er. 
