the Ash of Armeria maritima. 267 



inorganic constituents; in fact the only plants which arc so are 

 the maritime plants ; in the ashes of which we invariably find 

 iodine and bromine, two substances which are not generally met 

 with in the ashes of other plants *. All other plants on burning 

 leave ashes which contain almost always the same number of 

 inorganic substances, but in different relative proportions. The 

 complexity of the composition of the plant-ashes with which we 

 have to deal in the investigation of the exact relations of the in- 

 organic matters to the growing plant, is the chief cause of the 

 great difficulty we experience in assigning to each of them its 

 proper function in the vegetable organism. It appears to me 

 that we cannot arrive at anything like a rational method of culti- 

 vation until we shall have become acquainted with the functions 

 of every one of the inorganic substances found in the ashes of 

 plants, and until we shall have learned how far one substance is 

 capable of replacing another in the vegetable organism; and 

 lastly, how far a change in the chemical composition of a soil 

 affects the natural habits of plants. I do not mean to say that 

 these are the only points which require to be settled, but I 

 consider them as questions, a satisfactory answer to which would 

 prove useful to practical agriculturists. 



With regard to the second question we possess several analyses, 

 which prove clearly that soda can be replaced by potash, and lime 

 by magnesia to some extent, and vice versa ; and as it appeared 

 to me useful to contribute a few facts towards our knowledge on 

 this subject, I took advantage of Dr. G. Wilson's kindness, to 

 whom my best thanks are due for the use of his laboratory, and 

 made a few ash-analyses of Armeria maritima, which I trust will be 

 found not without interest in several points of view. My atten- 

 tion was first directed to this subject by a " notice of the presence 

 of iodine in some plants growing near the sea," by l)r. Dickie of 

 Aberdeen, now Professor of Natural History in Belfast. The 

 author found by chemical examination of specimens of Armeria 

 maritima from the sea-shore, and of others from inland and higher 

 districts in the neighbourhood of Aberdeen, that the former only 

 contained iodine ; and having taken the precaution to wasb the 

 specimens previous to analysis, and having thus removed any 

 objections which might have been made, namely that the iodine 

 was derived from saline incrustations. Dr. Dickie has been led 

 to conclude that marine Algse are not the only plants which pos- 



* M. Chatin and several other French chemists, as well as Prof. Marehand 

 of Halle, have satisfactorily proved the existence of iodine in a great many 

 inland plants. The ashes of inland plants, however, by no means univer- 

 sally contain iodine ; those plants in which its existence has been proved, 

 further contain but mere traces of iodine, whereas this clement invariably 

 occurs in sea-weeds and other exclusively maritime plants, and always in 

 notable quantities. 



