16 THE BOOK OF NATURE STUDY 



On the other hand, plants which do not tolerate salt die if 

 grown in soil watered with a solution of only 2 to 3 per cent, of 

 common salt. This is true of all plants except those which belong 

 to saline habitats Halophytes, as they are called, and of a few 

 Non-Halophytes. If the structure of these salt-loving Non- 

 Halophytes be compared with that of Halophytes, the chief re- 

 semblances lie in the arrangements for preventing transpiration. 

 They have either a very thick epidermis, or abundance of hairs, 

 or incurved leaves with sunken stomata, or a reduced leaf surface. 

 They may have special arrangements for the storing of water, and 

 in this case the leaves will be succulent. Facts of this kind help 

 to explain the resemblance that undoubtedly exists between the 

 flora of high hills and that of the seashore. It is true that there 

 may not be salt in the air blowing over hills that are inland, 

 but this situation resembles that of the seashore in one particular, 

 namely, in the irregularity of the water supply. It has already 

 been noted that some few plants, like the Sea Thrift, belong to both 

 localities ; but even where the plants are not the same there is a 

 similarity of habit ; they are plants of low growth, and generally 

 of reduced leaf surface. 



The colour of plants by the sea is often deeper than that of the 

 same species growing inland in valleys. This is perhaps due to the 

 greater number of hours of sunshine which seaside places have. 

 It is well known that the colour of flowers is much more brilliant 

 in deserts, at high latitudes and on mountains where the sunlight is 

 intense and continuous. The dark blue of the Squill off the Cornish 

 coast, the golden yellow of the Gorse, the pink of the Sea Thrift, 

 seemed deeper than that of inland plants. It has been suggested 

 that the blue-purple colour needs the greatest amount of sunlight 

 energy, and white or yellow the least. From this point of view 

 the colours of the plants of successive seasons might be observed ; 

 many spring flowers are certainly yellow or white, whilst the 

 bluish-purple flowers belong to June and July. The Daffodil, 

 the Celandine, the Colt's-foot, the Buttercups are yellow ; the 

 Wood Anemone, the Starwort, the Daisy (Bellis) are white, and 

 these belong to spring ; the Cornflower, the Knapweed, the Self- 

 heal, the Vetches, and many another are bluish-purple, and flower 

 in the summer months when sunlight is not only intense but of 



