118 THE RELATION OF PLANTS TO TIDE-LEVELS 
south, and 1,100 east) Spartina glabra occurs scattered among the Juncus. It 
seems to have extended, probably by rhizomes, from denser areas outside the 
belt. In all such cases it looks starved, and is not over 3 dm. tall. Between 
200 and 250 south, Spartina patens patches also contain Spartina glabra. There 
is no evidence of antagonism between the two. 
In smaller numbers and more restricted areas several interesting maritime 
plants occur in this belt. Gerardia maritima forms distinct beds. Where it 
occurs, the grass or rush is of very short stature, not over a decimeter, or may 
be wholly absent. Mud, often containing small pebbles, is visible between the 
plants. As the grass or rush gradually becomes taller around the Gerardia 
patch, the Gerardias become less numerous, taller (up to 2 dm.), and later in 
flowering. This is evidently due to shading of Gerardia by the competitor, 
reduction of light inducing taller growth, and reduction of temperature causing 
later germination and slower maturation. 
At 150 to 160 south, Gerardia is accompanied by the much rarer T'riglochin 
marituma. ‘This plant occurs only in the midst of the spots where competition 
is least. It never, in this belt transect, exceeds 1.5 dm. in height. The indi- 
viduals are numerous — a hundred or more in each patch. They seem healthy, 
and flower and fruit freely. At one place about a dozen plants of Plantago 
decipiens are mingled with Gerardia and Triglochin (160 south and 1,090 east). 
These were observed in two successive years. They seem healthy, but are of 
only medium size, about a decimeter tall. In other parts of the Marsh this 
species attains a height of 1.5 dm. with many leaves and inflorescences to each 
plant, and T'riglochin reaches a height of 2 or 2.5 dm. 
Spergularia marina was first met at 298 south and 1,075 east—an isolated 
plant. It is established on the mud-flats about 100 south, in this zone, and on 
the margins of the next. There were in 1909 about a dozen individuals, 0.6 to 
-0.8 dm. tall, flowering and fruiting freely. This species and Plantago decipiens 
occur in greater luxuriance outside our belt transect on the inner margins of the 
Spartina glabra zone, where the mud is very sparsely settled by other plants. 
Spergularia was observed in our strip in these places and only in these, both in 
1909 and 1910. 
Scirpus nanus, miniature but full grown, forms a bed at 122 south and 1,089 
east. It is in the edge of a mud-flat, along with Distichlhs, Salicornia europea, 
and Atriplex patula hastata. This is much more exposed to sun and wind than 
the place it occupies in the inner border of the seventh belt. 
The scattering plants named above are all essentially gregarious, and not 
found everywhere. The following are very common members of the vegetation 
of protected shores, but occur often as isolated individuals: 
Salicorma europea makes its first appearance in the edge of the first large 
tide-pool (315 south by 1,075 east). In the area from 250 to 300 south many 
Salicornias were dead in 1909, apparently eaten by grasshoppers. Other 
individuals gave evidence of “ damping-off” at the base. The first healthy 
plants were 282 south and 1,085 east. Between 150 and 100 south many 
Salicornias were large and bushy—excellent specimens of the species. But 
others were dying at the tips, and some were quite dead. Even the best condi- 
tions south of 100 feet are evidently unfavorable to this species. 
