• SUGAR FROM THE ROSEBAY, ggg 



it is likewise the cause of the difference of the proportions 

 of the principles of sulphate of barytes given by the che- 

 mists, who have attempted at different times to determiue 

 its composition. 



XIII. 



ffote on a Species of Manna, or concrete Sugar, produced by 

 the Rhododendron Ponticum*. 



Few years ago Messrs, Fourcroy andVauquelin remark- Concrete su- 

 ed, that a concrete sugar, or manna, exuded from the re - » arontlieroseY 

 ceptacle of the flowers of the pontic dwarf rosebay. 



Mr. Bosc has lately observed it afresh, and presented to described. 

 the Institute some grains of this substance collected by him 

 from the receptacle of the fruit, several of which were up- 

 ward of £ mill. [0*79 of aline] in diameter. Their taste and 

 appearance do not differ perceptibly from the purest sugar- 

 candy; but it is necessary to be on our guard against this 

 appearance, on account of the deleterious properties sus- 

 pected in the plant. Mr. Deyeux has even found, that they 

 leave an acerb smatch on the palate. 



The manna of the rosebay, according to Mr. Bosc, isdis- Reasons why 

 solved during the night by the moisture of the atmosphere, seldom seen « 

 melted in the day by the heat of the sun, and does not ex- 

 ude from plants that vegetate vigorously. These are the 

 reasons why it is so seldom seen. Plants growing in pots, 

 and sheltered from the dew as well as from the sun, are most 

 likely to furnish it. The grains above mentioned were col- 

 lected from a plant, in which, all these circumstances united. 



Mr. Bosc intends, if possible, to collect a sufficient quan- 

 tity to analyse. 



* Annales de Chimie, vol. LXIII, p. 102. 



XIV. 



