9 o THE FACTORS [Part I 



of large quantities of salt in their nutritive solution and thus experience a material 

 diminution in their assimilation. Stahl's supposition that halophytes possess stomata 

 that are always rigidly open is not confirmed by O. Rosenberg's more recent investi- 

 gations. The share taken by stomata in transpiration might therefore be generally 

 less than Stahl believed himself entitled to assume. 



ii. HALOPHYTES 1 . 



The amount of salt contained by halophytes is not exclusively determined 

 passively by that of their substratum, but depends chiefly on a craving for 

 salt in the plant itself, since plants that naturally grow in such localities are 

 in ordinary soil also in the habit of storing up larger quantities of sodium 

 chloride than most non-halophytes. There are however, even among the 

 latter, a few species with this tendency, which is always combined with the 

 ability to support larger quantities of salt than other plants can endure. 

 Many of these salt-loving species growing in ordinary soils appear 

 occasionally on the sea-shore and in other habitats the salinity of which 

 keeps other plants at a distance. 



Thus the roots of Beta vulgaris, according to several analyses, contain as much 

 as 35-45 % of chlorine in their ash. In a Cochlearia grown on sandstone 4170% 

 of chlorine was found ; Crambe maritima grown on manured land took from it 

 15-46% ; Apium graveolens up to 22-14% ; Asparagus officinalis, a facultative halo- 

 phyte, up to 15% ; E^ngium maritimum up to 19-30%. In the ash of the horse- 

 radish, however, in the root only 1-78%, in the leaves 5-54 %, of chlorine was found. 

 The micro-chemical examination for chlorine in the leaves of Indian halophytes 

 cultivated without salt in the Buitenzorg botanic garden gave an intense reaction 

 in fourteen cases and only a weak one or none at all in seven cases. 



It is worthy of note that halophytes are by no means uniformly distributed among 

 all the families of plants, but rather occur plentifully in certain families, while in 

 others there are few or none. Certain families consist chiefly of halophytes, 

 as Chenopodiaceae, Frankeniaceae, Plumbagineae, or contain large numbers of 

 them, as Amarantaceae, Aizoaceae, Cruciferae, Tamaricaceae, Malvaceae, Euphor- 

 biaceae, Umbelliferae, Rhizophoraceae, Lythraceae, Papilionaceae, Convolvulaceae, 

 Compositae. Of families and groups which dislike salt may be mentioned : 

 Amentaceae, Piperaceae, Urticineae, most Polycarpicae, Rosaceae, Melastomaceae, 

 Ericaceae, Orchidaceae, Araceae, and the Pteridophyta and Bryophyta. 



According to our present data, it would appear as if the representatives of 



amilies inclining towards halophily were generally richer in chlorine than those 



of salt-avoiding families. The comparison between the contents of chlorine in both 



groups of families taken from Wolff's ' Ash-Tables ' is in favour of this view. But the 



material in hand is not yet sufficient to warrant final conclusions. 



As has been stated before, halophytes can thrive on ordinary soil, for 

 instance on garden-soil, without any addition of common salt. Indeed some 



1 Schimper, II. The older literature is there cited. 



