74 THE PLANT WORLD. 



tion of Mutation Ijy Artificial Stimulation." " New Mutants of the Even- 

 ing Primrose." 



W. A. Cannon : " Topography of the Chlorophyll-apparatus of Some 

 Desert Plants." 



D. S. Johnson : " A New Type of Embryo-sac in Pcpcromia." 



E. C. Jeffrey and Arthur Hollick : " Affinities of the Cretaceous Plant 

 Remains referred to the Genera Dammara and Brachyphyllnvi. 



B. J. Howard: "The Tannin Cells of Persimmon." (By invitation.) 

 V. M. Spalding: "Some Problems in Desert Botany." (By invitation.) 



The Production of Oil of Wintergreen. — While oil of 

 wintergreeii was formerly made b}' distilling an etherial oil found 

 in the leaves of the wintergreen (Gaiiltheria prociimbeiis, Linn.), 

 the cost of gathering this plant became prohibitive. Now " oil 

 of wintergreen " is made by distilling the etherial oil found in the 

 bark of the sweet birch (Betula leiita, Linn.). " The wholesale 

 chemists refine it and sell it as ' essential oil of wintergreen." This 

 is the natural oil. 'Artificial oil ' is made by a purely synthetic 

 process in the laboratories. Chemically it is exactly the same, 

 and being produced at less expense sells at a much lower price. 

 — Forestry and Irrigation. 



