THE AMERICAN BOTANIST 85 



often washed u\) by tlie waves and gathered as sea weeds by 

 the uninitiated. Tt has sometimes been reported that the 

 Japanese air plant is a sea-wetd of the genus Demurest ia, but 

 it is certain that the bulk, if not all, of the specimens offered 

 for sale are not sea-weeds. Possibly a variety of sea products 

 are used in this way. The specimens are dried and then dyed 

 a bright green, and ni course do not grow, though many peo- 

 ple will be found to assert that they do. ^^'e are indebted to 

 Dr. E. F. Bigelow, for the itlentity of the specimens. 



Chemicals Excreted by Plants. — Since plants cannot 

 select the minerals composing the soils in which they grow, it 

 must often happen that there enters the plant along wdth more 

 useful substances, a number of useless or even harmful 

 minerals. Or it may be that the plant, in forming some neces- 

 sary product, will have left over as a by-product, more or less 

 chemical matters that must be disposed of. These are taken 

 care of in various ways. Sometimes they are formed into 

 crystals and stowed away in the cells of the leaf, or they may 

 be isolated in the bark, the wood or in the latex of the plant. 

 Some few plants have the facult_\- of excreting some of these 

 substances which may be found as incrustations on the surface 

 of the leaves. Various species of the sword fern (Nephro- 

 Icpis) excrete lime at the tips of the veins, and A. B. Klugh 

 reports in Rhodora the excretion of salt b)^ a salt meadow 

 grass — Spartiua glabra alterniflora. Whether such excre- 

 tions are of benefit to the plants is still a Cjuestion. Some 

 botanists are of the opinion that they may aid the plant in se- 

 curing" water from the air under certain conditions. 



