NOTE and COMMENT 



Lignum Nephriticum. — Three or four centuries ago, 

 the dabblers in science discovered a remarkable tropical wood 

 which had the property of causing pure water in contact with 

 it to become highly fluorescent. If chips of the wood were 

 placed in water, or if water was poured into a goblet made of 

 the wood, it became golden yellow in sunlight and a beautiful 

 peacock-blue by reflected light. This curious property was 

 assumed to be indicative of medicinal properties in the wood 

 and its use in kidney troubles soon earned for it the name of 

 lignum nephriticum. Although known for so long, the exact 

 botanical identity of the plant that supplied the wood has re- 

 mained in obscurity almost up to the present. From the inves- 

 tigations of W. E. Safford of the United States Department 

 of Agriculture, it now appears that the wood of more than one 

 plant has the power to make water fluorescent. The best 

 known of these is probably the Mexican shrub, Eyscnhardtia 

 polystachya, but a Philippine species, Pterocarpus Indicus, is 

 nearly as renowned. Since the genus Picrocarpus is also rep- 

 resented in Mexico, it is possible that other species there have 

 similar properties just as other species of Pterocarpus in the 

 Old World are known to have, though in a lessened degree. 



Growth Periods of the Elm. — In spring, the elm buds, 

 •like those of other trees, throw off their protecting scales and 

 by a lengthening of the internodes in the bud and the develop- 

 ment of the embryo leaves forms leafy twigs a foot or more 

 long. In the woody plants of the tropics, growth may proceed 



