8 Dll. NICHOLS ADDRESS. 



It was formerly tho't bj chemists that plants lived upon humus, a com- 

 pound entirely organic in its nature, and when some metals were found 

 in the ash of plants, they were regarded as accidental ingredients, or 

 extraneous bodies which somehow intruded themselves into the inciner- 

 ated mass. In our time we know that these mineral bodies enter the 

 vegetable structures as food, and that they cannot exist without them. 

 The mineral portion of plants is small indeed,, compared with the nitro- 

 genized and carbonaceous parts, and this paucity of the mineral sub- 

 stances was, undoubtedly, the reason why the early experimenters were 

 led into error. At present, we are aecjuainted with sixty -five elements 

 or primary bodies, of wdiich all things, animate and inanimate, are 

 made. Twenty-two of these have been found in plants, and therefore 

 are to be regarded as food material. Let us for a moment consider 

 the strange metals and other substances which plants absorb into their 

 structures. Among the metals, we find iron, potassium, calcium, so- 

 dium, magnesium, manganese, copper, C333ium, rubidium, and zinc. 

 It has been stated that arsenicum has been found in plants, but this is 

 doubtful. The non-metals are iodine, bromine, fluorine, chlorine, phos- 

 phorus, silicon, carbon, hydrogen, nitrogen, oxygen and sulphur. 

 Nothing can appear more singular than the fact that the refractory 

 metal, iron, can find its way into the stalk and leaves of plants, or that 

 the rarer metals should be hunted out of the soil by them, and apjDro- 

 priated as food. Some varieties of plants have peculiar appetites, and 

 require most extraordinary elements, in order to thrive. Tobacco is 

 one of them, and the ash which clings to the end of the smoker's cigar 

 contains substances found in but one or two other plants known to 

 man. Among the rarer bodies are the newly discovered metals caesi- 

 um and rubidium, and how, or where the plant obtains them, isin-» 

 deed a mystery, as the most delicate chemical tests have failed to de- 

 tect these elements in soils. In common garden beets, also, the same 

 substances have been found. Copper has frerjuently been observed in 

 vegetable products used for food, and what is very singular, the metal 

 has recently been discovered in the feathers of birds, and some of the 

 tints in the plumage are due to its presence. The fiuorine which is 

 found in the enamel of teeth in men and animals, comes from plants, 

 as does also the manganese which accompanies iron in the blood. 

 Aluminium, the metal which v/ithin a few years has been regarded 

 with special interest as of great service in the arts, has been found in 

 certain species of lycopodium, and zinc in the viola coliminaria, a plant 

 common to some sections of France. Bromine and iodine are found 

 in the marine al^j\}, or seaweeds, and for a long time all of these impor- 

 tant substances employed in medicine and the arts, were derived from 

 sea plants cast upon shore by the v/aves. 



^ The organic; constituents of plants, elaborated or formed from com- 

 binations of the elements, carbon, hydrogen, nitrogen and oxygen, 

 make up the largest portion of their bulk, and therefore must be 

 regarded as of essential importance as food. Before considering the 

 sources and value of these agents, to vegetable structures, it will be 

 interesting to examine briefly the conditions under which plants start 



