Such terms as hydrophytes, xerophytes, and halophytes had been used by plant geographers before Warmings time e.g., by Schouw;4 and the terms evidently supply a want felt by botanists as they have come into general use.
The criticisms were directed chiefly to the inclusion of sand dune plants among halophytes, to the exclusion of halophytes from xerophytes, to the inclusion of bog xerophytes among hydrophytes, to the inclusion of all conifers among xerophytes and of all deciduous trees among mesophytes, and to the group of mesophytes in general.
A considerable proportion of halophytes are succulents, i.e.
Some halophytes tend - to lose their succulence when cultivated in a nonsaline soil; and some non-halophytes tend to become succulent when cultivated in a salty soil; there is, it need scarcely be stated, little or no evidence that such characters are transmitted.
Similarly, the small amount of cuticular and of epidermal protection, and of lignification in succulent halophytes may also be related to the same circumstance.
Forms of stone cells or stereids occur in some of the more suffruticose halophytes, as in Arthrocneniumglaucum.
The interesting occurrence of certain halophytes and hemi-halophytes on sea-shores and also on mountains is probably to be explained by the past distribution of the species in question.
In the west of Ireland and in the Faroes, where certain inland and lowland localities are still uncultivated, Plantage maritfma and other halophytes occur in quantity and side by side with some Alpine species, such as Dryas octopetala.
There has, however, been performed upon halophytes very little physiologically experimental work which commands general acceptance.