Delf \ — Transpiration in Succulent Plants . 427 
serving the chloride content relative to the total ash content, as well as 
relative to the fresh weight. Benecke’s figures show clearly that, although 
there is an apparent diminution of chloride content owing to the changes in 
water content of the plant, there is no change in the actual proportion of 
chloride present in the ash. The whole theory of diminution and dis- 
appearance of the chlorides, through the intervention of organic acids, thus 
stands at present unsubstantiated by facts. 
Lesage 1 was the first to show clearly that it is the saline character of 
the habitat which appears to chiefly cause the succulent character of the 
leaves of halophytes. No less than ninety species found near the coast were 
examined, representing thirty-two families. Of these fifty-four had leaves 
thicker by the sea than when inland, twenty-seven were indifferent, and four 
were thicker inland than by the sea. Of the fifty-four which showed increase 
in fleshiness from the more saline position, some were oftener found inland 
than by the sea (and may be termed ‘facultative’ halophytes), such as 
Solanum Dulcamara , Plant ago Coronopus , and Ranunculus sceleratus , and 
some were typical littoral forms, as Beta maritima , Cakile maritima , Glau - 
cium luteum , and Arenaria peploides ; a few species, although littoral, were in- 
different, as Psamma arenaria, Suaeda maritima, and Triglochin maritimunr 
With the exception of the few species mentioned, there was a distinctly 
greater fleshiness in the littoral than in the inland forms. 
Most of these plants have no definite aqueous tissue, and their succulence 
is brought about by an increase in the number or size of the mesophyll 
cells. Thus the mesophyll cells of Parietaria appeared to increase in size, 
those of Ranunculus sceleratus increased in the number of layers, whilst 
Beta maritima, A triplex portulacoides , and Cakile maritima showed increase 
in both number and size of the cells. Unfortunately, no mention is made 
of aqueous tissue as such, although the observation is made that in some 
cases the chloroplasts become paler and fewer in the plants grown in salty 
substrate. However, there is little doubt that some of these interior cells 
with little chlorophyll function as water-storing tissue, especially in plants 
with fleshy leaves, susceptible to salt content, such as Salicornia , Cakile 
maritima , and Arenaria peploides ; there is little doubt, also, that this 
colourless water-storing tissue tends to increase in saline situations. Ob- 
servations were supplemented by culture experiments with Lepidium sativum 
and other plants which could endure saline solutions, when it was found 
that, in general, the more concentrated the solution the more fleshy were 
the leaves produced. 
Some experiments of Holtermann throw further light on the question 
of the effect of the salt content of the habitat in the Mangrove vegetation 
of Ceylon. A number of Mangroves (. Lumnitzera , Avicennia , Rhizophora , 
1 Lesage, P. : Recherches experimentales sur les modifications des feuilles chez les plantes 
maritimes. Rev. Gen. de Botanique, 1890. 
