Experiments on Absorption of Salt-Marsh Plants. 139 
That the amount absorbed in this way can in no way replace 
normal absorption is shown by the facts recorded in 1906, when it 
was pointed out that the plants, probably because of the very dry 
summer, had only grown to about half the height they had attained 
the year before. 
The water absorbed by its aerial parts must pass into the plant 
by osmosis through the epidermal cells and these are so formed 
that their walls offer little resistance to its passage. Both in Suceda 
and Salicornia the walls of these cells are unthickened and are 
covered only by a thin cuticle comparable to that found in Zoster a > 
The presence of large cellulose tracheal-like cells in some species of 
Salicornia has long been known. These cells run from the aqueous 
tissue surrounding the stele, through the palisade tissue and in 
some cases came into contact with the epidermal cells. They are 
isolated from each other and from the anastomosing vascular system 
of the succulent tissue. Various functions have been assigned to 
them. Ganong suggests that they are air-storing tracheids, 
Warming and others that they are for water-storage, but it is 
now suggested that it is possible that their function is to facilitate 
the passage of the water absorbed by the epidermis to the aqueous 
tissue. This, however, is only a suggestion, as further experiments 
must be made to elucidate their function. 
I wish here to express my thanks to Miss E. N. Thomas and 
to Professor F. W. Oliver for their helpful criticism of this paper. 
