416 Observations on Structure in the Ashes of Plants. 



hibiting a series of squares. The vegetable forms which are 

 respectively furnished by the BIyth, Newcastle, and Barnsley 

 coal appear to be so different, that I think by the aid of the 

 microscope it would be almost possible to assign an unknown 

 specimen to its proper locality; and this possibility cannot 

 but have its due weight with the geologist. From these facts 

 it is evident that the true framework and basis of vegetable 

 structure in the plants of coal is not only entirely independent 

 of carbon, but that it has also resisted the bituminous decom- 

 position which has converted all the carbonaceous materials 

 into a highly inflammable substance. 



I find, upon further investigation, that silica is not the only 

 material which forms the framework of plants. Lime and 

 potash also occur as vegetable skeletons. The ashes of the 

 calyx and pollen of the mallow, for instance, consist of organ- 

 ized lime, and the ashes of the petals of the rose consist of 

 organized potash. The latter quickly deliquesce, and upon 

 the addition of nitric acid, permanent, crystals of nitrate of 

 potassa are readily formed. The ashes of the pollen of the 

 geranium also consist of potash. Hence, it is no longer " a 

 great question," to use the words of Dr. Dalton, " whether 

 potash is a constituent principle of vegetables or formed du- 

 ring their combustion*;" for it is evident, from the facts now 

 adduced, that potash, lime, and silica equally enter as organ- 

 izable products into the structure of plants. 



In consequence of the medicinal properties of some plants 

 being similar to those of the fixed materials which enter as 

 organizable products into their structure, perhaps we may 

 fairly ask if there be any necessary connexion between the 

 medicinal properties of plants and the nature and properties 

 of their solid materials. It is obvious that this question could 

 not be entertained so long as the solid materials of plants, 

 carbon alone excepted, were looked upon as foreign matter, 

 accidentally introduced. 



It has been objected by some to whom I have communi- 

 cated my opinions that the siliceous structure in the ashes of 

 gramineous plants arises from the agency of heat and is due 

 to crystallization ; and others again have supposed that the 

 process of respiration not only causes a large deposition of 

 silica on the epidermis, but also leaves a similar coating upon 

 the organs of the vascular tissue. The first of these objec- 

 tions is at once and easily removed by showing that in an un- 

 burnt portion of the husk of oat, for example, when placed in 

 Canada balsam, we can trace the very same series of siliceous 

 columns which the burnt specimen exhibits ; and that, in fact, 

 the similarity is so great that they have often been mistaken 

 * Dalton's Chemical Philosophy, vol. i. p. 472. 



