180 ANNUAL OF SCIENTIFIC DISCOVERY. 



generally shows a clear gray, or slightly mottled fracture. Mr. Stir- 

 ling considers that, while color is admissible as a test of strength, it 

 is not so of chemical constitution. The fluidity of Berlin iron is due 

 to the presence of arsenic. Manganese mixed artificially with cast- 

 iron closes the grain, and is an improvement to that as well as to 

 steel. Manganese in wrought-iron gives it the hot-short property, 

 whilst the cold-short is produced by phosphorus ; the admixture of 

 arsenic renders wrought-iron hard and brittle. 



EXISTENCE OF IODINE IN FRESH-WATER PLANTS. 



MULLER some time since discovered iodine in the water-cress, and the 

 confirmation of this, in respect to this plant growing near Paris, con- 

 vinced M. Chatin that this body is not, as is usually thought, confined 

 to the zone of saline waters or mineral springs. He first examined 

 various other species of Cruciferae, under the idea that most of these 

 might contain it as they do sulphur and nitrogen ; but the only one in 

 which he detected it was another aquatic, the Nasturtium ampJiibhim. 

 He then turned his attention to the fresh-water aquatics, and, with 

 some modifications in its mode of existence, found it present in an im- 

 mense number of plants. Some of the results of the investigation are 

 thus stated : Iodine exists in all aquatic plants, while it is absent, or 

 at all events cannot be detected, in terrestrial plants. Plants living in 

 running waters, or in large masses of water capable of agitation by 

 the winds, contain more iodine than do those in stagnant water. It is 

 found also, though in small quantity, in those plants which are only 

 imperfectly immersed in water, or during only a portion of their lives. 

 The same plants which contain iodine when growing in water do not 

 contain it if developed out of it. The proportion of iodine in plants 

 is in general independent of their nature, and solely subordinate to 

 their habitat, as shown by the Conferva, Nympfuzee, Ranunculi, &c., 

 which are all equally rich in iodine in running waters, and all equally 

 poor in ponds and marshes. An examination of the juices of these 

 plants, and of their parenchyma, proved that the iodine existed ex- 

 clusively in the former, and therefore as a soluble iodide. In answer 

 to the questions, why land plants are destitute of it, and why it varies 

 so greatly in the fresh-water ones, it may be observed, that iodine can 

 scarcely exist in appreciable quantities in the small quantity of water 

 that gains access to terrestrial plants ; and the different position of the 

 aquatic ones, in respect to soils, &c., which may contain it, will ac- 

 count in some measure for the variations. As iodine is found, not only 

 in the plants growing in large rivers, but in those of every rivulet, 

 pond, and marsh, it is impossible that it can be derived from any min- 

 eral spring, but must be widely diffused over the earth, accompanying 

 like a satellite the chlorides, with which it is extracted by the water. 

 Among the plants analyzed by M. Chatin, and on which are founded 

 the previous results, are enumerated the cabbage, the horseradish, 

 and the radish, terrestrial Cruciferse which contain no iodine, and 

 various aquatic plants which contain more or less iodine, the cress, 

 Conferva, Charafoctida, Sagittaria, Potamogeton, Ranunculus aquatilis, 

 and many others. Comptcs Rendus, March 52. 



