326 DR. SARAH М. BAKER AND MISS М. H. BOHLING ON 
Page 
(c) Vegetative Reproduction (неее, 361 
A. Abortion of Sexual Organs cce 361 
Factors eliminated. 
Distribution of Fruiting Specimens. 
Effect of Shade on Reproduction. 
The Humidity Factor. 
Application to exceptional cases. 
Application to F. ceranoides. 
Stimulus for the Production of Sexual Organs. 
B. Vegetative Budding........ ecco 365 
The Cryptostomata of F. vesiculosus megecad limicola ................ 367 
Application of these Principles to the Morphology of the Loose-lying 
Fuci ............ зави ниве eie] aha esee sehen 367 
Application of these Principles to the Morphology of the Sargasso 
weed users see esse 369 
PART 3.—Ом THE RELATIVE DISTRIBUTION oF THE Marsu Fucorps., 
(a) Pioneer Vegetation „еее еее еее nnn 371 
(b Undergrowth .................. pessssesesesseveteecenueceshinseevees 372 
Vertical Zonation, 
Distribution in relation to Salinity, 
Epiphytes and Undergrowth. 
(c) Covering Vegetation after Erosion .................................. 375 
General Summary .............\..... не 376 
Literature 4... esse $... 9/9 
GENERAL INTRODUCTION. 
THE very luxuriant and extensive undergrowth of Pelvetia canaliculata 
у. libera found by Prof. К. W. Oliver (Oliver, in Tansley, 1911, р, 364) in 
the great Salicornia marsh at Blakeney Point, Norfolk, has already drawn 
the attention of one of us (Baker, 1912) to the possibilities of the salt marsh 
as a habitat for Brown Algæ. A somewhat analogous association has been 
recognised by Cotton on the Peat Marshes in Achill Sound and Bellacragher 
Bay, W. Ireland (Cotton, 1912, p. 80), in which a minute form of Fucus, 
Г. vesiculosus v. muscoides, Cotton, forms a dense mossy carpet with Glyceria, 
Armeria, and Salicornia. Cotton has also especially noticed the associations 
of Brown Algæ, Fucus volubilis and Ascophyllum nodosum v. minor, occurring 
in great profusion on the salt marshes between Keyhaven and Hurst Castle, 
Hants, among Spartina Townsendii (Cotton, in Morris, 1914, p. 192). 
It is evident that the occurrence of the larger Brown Algæ on salt marshes 
is by no means occasional or accidental, and the investigations to be described 
in the present paper have been directed primarily to a study of the effects 
of the physical conditions, characteristic of the salt-marsh habitat, upon 
the morphology of these normally rock-dwelling Algæ. The causes of the 
great changes in morphology induced by this change of habitat have been 
