298 l Proc - B.N.F.C., 



The lecturer introduced the subject by saying that the word 

 " Dendrite " was derived from the Greek root dendron, meaning a 

 tree. A Dendrite was a tree-like growth of an inorganic substance, 

 and the occurrence of such growths in stones gave rise to the 

 expression "picture-stones," because the Dendrites had the 

 appearance of having been painted or printed upon the stone. 



Dendritic growths of minerals were well-known to all who 

 had even the slightest acquaintance with the subject of mineralogy, 

 because these growths were beautiful and attracted the attention 

 of the nature student. The semblance of life in stones was a 

 very real phenomenon and a never-failing source of wonder and 

 admiration to every mineralogist. Dendritic growths had often 

 been seriously attributed to organic agencies, in times past, by 

 experienced scientific workers, but there was now no doubt 

 whatever that they were due to the vagaries of crystalline activity. 

 A flower had a definite form and habit, and every mineral had 

 also its own peculiar crystalline form and habit, and there was a 

 remarkable semblance between dendritic, arborescent, and mossy 

 growths of minerals, and the lower forms of vegetable life. 



In a moss-agate, for example, the exquisite green, red, and 

 brown growths of chloritic minerals embedded in clear translucent 

 chalcedony bore much more than a fanciful resemblance to a 

 growth of some algae in a clear pool of water. Again, the 

 beautiful dark-brown or black dendritic growths of oxide of 

 manganese in the variety of agate, known as " mocha-stone," 

 had the appearance of delicate ferns. A microscopic examination 

 of Dendrites soon distinguished them from vegetable substances, 

 but nevertheless did not detract from their interest ; the growth 

 of crystal upon crystal was just as wonderful in its own sphere 

 as the growth of cell upon cell in the Vegetable Kingdom. The 

 ultimate structure of a crystal was perhaps as great a problem as 

 the ultimate structure of a single cell of living matter. 



Dendritic growths were capable of an arbitrary division into 

 two classes which Mr. Strachan proposed to call (1) free dendrites 



