1915] ROBERTS—BEACH PLANTS 409 
separated from Vineyard Sound by a high shingle mound. Among 
the shingle Cakile edentula grows most luxuriantly and forms thick, 
hedgelike masses. They are the most abundant and thrifty plants 
seen. Here the entire shingle strand must be washed often by the 
summer storms. 
The relationship of the plants found at the base of Nobska 
Cliff and Falmouth is the same as that found on the beaches, but 
.the tide lines are nearer together there, and the zones are con- 
densed. The telescoping comes in the zone between the summer 
storm tide line and the winter drift, so that there is a more sudden 
transition from the succulent zone to the Ammophila zone, prac- 
tically eliminating the transitional zone. 
The low sea cliffs, at whose base the lower beach is eliminated 
and where there is living Zostera marina, as at Lackey’s Bay, furnish 
an additional grouping. Here, on what corresponds to the plant- 
less lower beach, is a grouping of Zostera marina and Spartina 
glabra pilosa. Their advance is checked by a mass of dry eel grass 
three feet in depth, but on the top of the eel gras, as on the sub- © 
stratum of the lower middle beach, is a grouping of succulent plants 
with exceptionally long roots. This is a strictly succulent zone, 
for the Ammophila does not advance beyond the eel grass débris. 
Why succulents can grow on the eel grass substratum and Ammo- 
phila not is an interesting question. 
Along the cliffs where Zostera marina is present and the lower 
beach is covered by water, the following new forms are found: 
Suaeda maritima, Salicornia europaea, Limonium carolinianum, 
and Ligusticum scoticum. Their ecological relationship is shown 
on the chart. The last three divisions of the chart show what 
GANONG (5) speaks of as a Salicornia-Suaeda association. CHRYS- 
LER (3) gives a list of plants arranged in a descending scale with 
respect to salt-resisting capacity, and in this Salicornia europaea 
is next to Limonium carolinianum. GANONG found that the root 
hairs of Salicornia europaea can endure go per cent of sea water 
without plasmolysis, and those of Suaeda maritima 60-70 per cent. 
CANNON (2) refers to salt-containing places as having marked 
zonal distribution; several species of Aériplex and Suaeda are 
nearer the center of salt spots, where the concentration of salt is 
highest. 
