376 DR. SARAH М. BAKER AND MISS М. H. BOHLING ON 
disintegration of these hummocks, and not infrequently their flat upper 
surfaces become infected with the spiral Fucus vesiculosus from the marsh, 
Salicornias and Asters may follow this, and so the hummocks may be 
gradually raised again to the level of the marsh. 
GENERAL SUMMARY. 
The origin of the Fucaceous vegetation, which is often a conspicuous 
component of the salt-marsh flora, is primevally the attached Fucaceous asso- 
ciation of the rocky shore. The production of a salt-marsh variety from a 
saxicolous plant may be brought about in two ways: either by direct vegeta- 
tive budding from detached fragments of the thallus, or by the modification 
of young plants germinating upon a salt marsh. Each individual species 
undergoes a series of striking morphological modifications in the transition 
from rock to salt marsh, and the adaptational varieties so produced are 
designated “ ecads,” according to the nomenclature introduced by Clements 
in 1905 ; they are persistent through many vegetative generations. When 
the modifications were critically examined, it was found that, in all the five 
species represented on the salt marsh, the modifications induced by the new 
conditions were of the same general type. Hence the several marsh ecads 
produced by each species were grouped together under a “ megecad limicola,” 
which included all the marsh-dwelling Fucoids as distinguished from those 
of saxicolous habit. 
The characteristics of the “ megecad limicola ” are, briefly :— 
1. Vegetative Reproduction. 
2. Dwarf Habit. 
3. Absence of Attachment Disc. 
And in the salt-marsh formation, but not in the loose-lying formation : 
4. Spirality or curling of the thallus. 
Of the seven species of Fucaceæ occurring in the littoral region of the 
English coast, four—namely, Pelvetia canaliculata, Ascophyllum nodosum, 
Fucus vesiculosus, and Fucus ceranoides—form varieties which may be 
classified under the megecad limicola. Fucus spiralis is only represented 
on the marsh by its variety nana, which cannot be regarded as a true salt- 
marsh variety. It was shown that all the dwarf spiral forms of Fucus as 
well as the turf-like and filiform Каст, occurring on our salt marshes, are 
referable to the megecad limicola of Fucus vesiculosus. These very dwarf 
forms are parallel to, but not identical with, the three dwarf forms of 
Fucus vesiculosus found in the loose-lying formation of the Baltic—ecad nanus, 
ecad subecostatus, and ecad filiformis. To avoid confusion, a new name, 
