VEGETATION OF DUNES AND SANDY HAMMOCKS. 131 
The slender, wiry culms of this grass, 3 to + feet high, with svanty 
involute rigid leaves, when bending under the burden of the iarge, 
more or less contracted, panicles of the broad, many-flowered 
drooping spikelets, render the species one of the most  strik- 
ing types of psammophile plants. It inhabits the dunes from the 
southern frontier of Virginia through North Carolina south to Texas 
and the Mexican coast. By its stout running rhizome, deeply buried 
in the sand and sprouting from the rather distant nodes, a single 
plant soon colonizes the bare dune. The flowers appear to be mostly 
infertile, as no spikelets with well-matured grain have been observed 
in the specimens from our coast. Jpomoeca carnosa, similar in its sub- 
terranean stems and root system to the above grass, is not infrequently 
found along with it, the numerous long prostrate stems bearing bright- 
green leaves, which cover the sand. Opuntia crus-corwi and Siphony- 
chia erecta are not rare in the same localities. The dead tops and 
branches of the sand pine (P/nws clausa) and tops of the Spanish dag- 
ger (Yucca aloifolia), with the trunks almost completely buried in 
the drifting sands, increase the impression of aridity on these desolate 
shores. 
Mesophile plant associations of the dunes.—In the shallow sandy pools, 
formed mostly by the accumulations of rain water in the depressions 
and rendered more or less brackish by the influx of the waves of the 
sea during storm tides, many of the plants of the semiswampy coast 
plain mingle with types of various families not found outside of the 
littoral belt. Of the former class occur the following, the first two 
being most frequent: 
Rynchospora torreyana. Linum medium. 
Hypericum aspalathoides. Scleria pauciflora glabra. 
Lechea torreyt. 
Of plants peculiar to the littoral belt occur: 
Scirpus americanus. Xyris torta pallescens. 
Fuirena scirpoidea. Cassia (Chamaecrista) mississippiensis. 
Scleria gracilis. 
Open groves of Cuban pines cover the flats behind the dunes, merg- 
ing frequently into the pine meadows of the coast plain. 
Xerophile plant associations of the sandy dry hammocks.—Between 
Bon Secour and Perdido Bay low, sandy hills or ancient dunes, rising 
above the saline swamps, support a high forest of evergeen trees, 
principally live oak, but with a mixture of laurel oak and Cuban and 
long-leaf pine. On these dry, sandy hammocks the sand pine (Pinus 
clausa), frequent in peninsular and western Florida, reaches its western 
limit. In this locality the tree has been found from 50 to 60 feet high, 
rarely over a foot in diameter, breast high. Stunted Spanish oak, 
barren oak, blue jack, and the common wax myrtle form the under- 
growth, and the procumbent stems of the saw palmetto deeply raoting 
