I goo- 1.] Effects of Water on Foliage Leaves. 329 



Summary of the results of the investigation : — 



There are four causes (in a measure quite distinct), which produce 

 the spotted condition of the tobacco leaf, due to : — 



(i) Fungi, (Cercospora, Macrosporium), Bacteria, Enzymes. 



(2) Conditions of soil, moisture, temperature, fertilizers, etc. 



(3) The recurrence of a philogenetic condition. (This is but a 



suggestion). 



(4) Local applications of chemical irritants. 



With regard to the last (4) the important points may be 

 enumerated. The alkali kills the tissue in direct contact with the 

 irritant ; it stimulates to abnormal development the tissue immediately 

 around the spot ; the cells outside of the stimulated area are drawn 

 upon more than ordinarily and are consequently poorer in protoplasm 

 and chlorophyll than that of the tissue in the ring, and in the tissue 

 of the ordinary part of the leaf 



The deductions to be made from this are, that plant growth may 

 be stimulated by local applications to leaves, that leaves can transport 

 the absorbed substance, and consequently the texture of the leaf may 

 be modified by artificial means. 



IX. — Some of the Effects of Sea-Water on the Air. 



The question as to whether the inorganic salts in solution in 

 sea-water ever pass off into the air, in the neighbourhood of the sea, 

 in any measurable quantity, has so far never received much attention 

 from scientific men, but it has long been suspected by many people 

 that sea-water does, in some way or other, enter the air, but little 

 has as yet been done in a scientific way to ascertain the nature of the 

 process, if any, by which the sea salt and other inorganic substances 

 may leave the solution and permeate the surrounding atmosphere. It 

 is obvious that, upon the occasion of storms and winds, the sea spray is 

 blown into the air, and if the air be below the saturation point, as 

 it generally is, much of the water evaporates while suspended in the 

 air, and in consequence, minute particles of salts are left floating in the 

 atmosphere, and later are blown about and deposited upon the surface 

 of the sea, or upon the land and the leaves of plants within a reasonably 

 short distance of the sea shore. Leaving this condition altogether 

 aside, it is still an open question whether the salt may be taken up 

 into the air without the aid of wind or spray and afterwards deposited 

 upon substances that have a physical contactile affinity for the salts ; 



