LICHENS. 65 



lichen starch, which is said to be intermediate in 

 composition and character between dextrine and 

 common starch. Dilute and boiling sulphuric acid 

 converts it into sugar, while nitric acid transforms it 

 into oxalic and saccharic acids. 



Lichen Manna. 



It is generally considered that the Israelites hi the 

 desert must have had previous knowledge of some 

 substance under the name of manna, and therefore 

 applied that name to the miraculous supply recorded 

 in Exodus. Be that as it may, substances having 

 different origins have long been known in the East 

 under the general name, and there has not been 

 wanting even the assertion that one or other of these 

 was the genuine " manna of the desert." To one only 

 of these substances does the scope of the present 

 volume permit us to allude, and that is a peculiar 

 form of lichen which has, from time to time, been 

 reported to descend like a shower cf rain. " Several 

 occurrences of what is called a fall of manna are 

 attributable to the accumulation of this lichen, 

 Lecanora esadenta. Aucher-eloi observed it in Persia, 

 in layers of nearly four inches in thickness. He sent 

 specimens, with the follov/ing note to France : ' In 

 1829, during the war between Persia and Russia, 

 there was a great famine in Oroomiah, south-west of 

 the Caspian. One day, during a violent wind, the 

 surface of the country was covered by a lichen, which 

 fell from heaven. The sheep immediately attacked 

 and devoured it eagerly, which suggested to the 

 inhabitants the idea of reducing it to flour, and 



F 



