1915] Knowlton,— Plant Societies at Roque Bluffs, Maine 147 
Of the above plants it is interesting to note the comparative abun- 
dance of Elymus arenarius on gravelly beaches. "This cireumboreal 
plant is now known along the coast to Casco Bay, the Isles of Shoals 
and Provincetown. Rosa virginiana deserves mention from its great 
abundance, its variability and the remarkable size and beauty of its 
flowers and glossy green leaves. Oenothera muricata is a very hand- 
some species here. The buds are massed at the top of the stem, 
appearing cymose, and often ten or a dozen will open at once, forming 
a ring of flowers. Mertensia maritima is a peculiar prostrate plant, 
with glaucous blue-green leaves, red buds, and blue flowers. It is 
occasional, but never abundant, on gravelly beaches. Galium A parine 
occurs in only two places, in loose shingle above high tide, and it has 
evidently been brought in ballast from further south. 
SALT MARSH. 
Zostera marina Juncus bufonius, var. halophilus 
Triglochin maritima “ Gerardi 
Agropyron repens Atriplex patula, var. hastata 
Agropyron caninum (L.) Beauv., Suaeda maritima 
var. tenerum (Vasey) Pease & Moore Salicornia europaea 
Agrostis alba Polygonum Fowleri 
Festuca rubra Stellaria humifusa 
Hierochloe odorata Spergularia canadensis 
Hordeum jubatum Ranunculus Cymbalaria 
Puccinellia angustata Potentilla pacifica 
Spartina glabra, var. alterniflora Limonium carolinianum 
S patens Glaux maritima, var. obtusifolia 
Carex maritima Plantago decipiens 
Scirpus americanus Aster novi-belgii, var. litoreus 
Juncus balticus, var. littoralis Solidago sempervirens 
“ — bufonius 
In the salt-marshes Carex maritima covers large areas so densely 
that other species are few. "The past season, however, after diligent 
search I found good specimens of the northern Stellaria humifusa, 
prostrate in the tidal mud between the stalks of the Carex in one of 
these areas. Juncus balticus, var. littoralis is the only salt-marsh 
species which seems able to compete successfully with other species in 
other habitats. It is frequent in swampy places some distance from 
the sea, and at one place I have found it in the shade of spruce trees 
at the edge of a peat-bog. 
