AND OF SALINITY. 269 



tween the moisture in the environment and the dark- 

 ness of colouring of certain animals. Thus he observed 

 that Molluscs such as Arion empiricorum (common 

 slug), Helix arbustorum, Succinea Pfeifferi, and Helix 

 circinata became darker than usual in moist localities. 

 He observed a similar condition also in certain Am- 

 phibia and in Lacerla vivipara. However, Eimer ob- 

 served just the reverse condition in Arion, finding 

 it darker upon the heights, where there was little water, 

 than in well-watered valleys. In any case, the effect is 

 probably an indirect one, acting through the vegetation. 

 The Effect of Salinity. The effect of salinity upon 

 members of the Vegetable Kingdom is well illustrated 

 by the peculiarities of form and structure possessed by 

 maritime plants. That these characters are at least in 

 part the direct effect of the salinity of the soil and at- 

 mosphere, is proved by comparison of plants growing 

 near the sea-shore with individuals of the same species 

 growing inland. Thus Lesage * has investigated no 

 less than 85 different species. He found that in 54 of 

 them the leaves were thicker in the maritime indi- 

 viduals than in the inland ones, they being about four 

 times as thick in Cakile maritima and Silene mari- 

 tima; in 27 there was no apparent difference, and in 4 

 they were thicker in the inland individuals. With re- 

 gard to the mesophyll, there was no noticeable change 

 in 11 species, but in all the other shore plants the pali- 

 sade cells were more numerous or attained greater 

 thickness, and at the same time the interspaces under- 

 lying the stratum of palisade cells were much reduced. 



*" Influence du Bord de la Mer sur la Structure des Feuilles," 

 Rennes, Oberthur, 1890. Also Rev. Gen. de Bot., torn. ii. p. 54. 



