484 



Scorching of Foliage. 



[Aug., 



air. Wiesner* found that in certain cases transpiration in a 

 wind may reach twenty times its value in still air, and that the 

 different behaviour of different plants depends largely on the 

 partial or complete closing of the stomata during wind! and on 

 the amount of cuticular transpiration. Though transpiration is 

 usually increased by wind, it may be reduced in certain cases, 

 as was found in Saxifraga sarmentosa, in which intercellular 

 transpiration was stopped by the rapid closing of the stomata, 

 and the cuticular transpiration was small. Young leaves, having 

 a relatively high cuticular transpiration, would show a large 

 increase in the amount of water lost through the cuticle during 

 wind, and this increase would often considerably more than 

 compensate for the reduction or cessation of stomatal transpira- 

 tion by the partial or complete closing of the stomata. Young 

 leaves may therefore be expected to be specially liable to wind- 

 withering. 



Injury by wind, being due to uncompensated loss of water by 

 the leaves, will depend on the combination of a number of 

 factors, viz., those favouring transpiration and those diminishing 

 the supplv of water to the leaves. Among the latter would be 

 dryness and coldness of soil, both checking absorption by the 

 roots. t It is easy to understand, therefore, that the effect of a 

 storm may depend to some extent on the character of the soil, 

 on the season of the year, and on the nature of the weather pre- 

 ceding the storm. § 



In this connection it may be pointed out that wind-borne salt 

 might in some cases be a factor indirectly favouring injury to 

 the foliage by wind. Supposing a considerable amount of salt 

 spray to soak into the soil during a gale, the absorptive power of 

 such roots as were reached by the salt would be temporarily 

 affected, II and the supply of water to the leaves would be inter- 

 fered with in consequence. 



* Wiesn'^r. Sifzh. Wien. AJ^ad., Vol. 96 (J887), ref. Just, Jahresbericht, Vol. 15 

 (1887). I, p. 216. 



f This does not occur in all plants. The stomata of Hydrangeahortensis were 

 found by Wiesner to remain wide open even during a strong wind, greatly 

 increased transpiration be^'ng the result. 



X Kihlman, Pflanzpn'hwl. Stndien ava Russisch Lappland, Acta Soc. Fauna et 

 Flora Fennica. Vol. 6. No. 3 (1890), p. 88 ; Molisch, tl7iters. iiher das Erfrxeren 

 der Pfanzen, :SejiQ.,\^%l. 



§ Vermont Agr. Exp. Stn.^ loc. cit. 



II The roots after a time would in most cases resume normal absorption, as 

 they would show a certain amount of adjustment of osmotic pressure. See 

 Schimper, Die indomalayhche Strandfora. 1891. p. 22. For an extreme case of 

 the phenomenon observed in the roots of certain halophvtes. compare Hill, New 

 Phytologut, Vol. 7, p. 133, and Vol. 8, p. 103. 



