LECANORA. 



229 



manna miraculously supplied to the children of Israel while 

 journeying in the wilderness. Several " rains of manna/' con- 

 sisting of one or other of these Lichens, have been described 

 by travellers as occurring in Persia and neighbouring coun- 

 tries. The manna is usually found in the form of small 

 lumps, from the size of a pin's head to that of a pea or 

 small nut, which are greyish or whitish, hard, irregular in 

 form, inodorous, and insipid, Individual plants weigh from 

 a few grains to about a couple of scruples when dry ; the 

 thallus bears no evidence of having, at any period of its 

 growth, been attached to a base of support. And, singularly 

 enough, analysis has failed to discover in it starch, though 

 it has detected no less than 66 per cent, of oxalate of lime 

 in some specimens ; hence it has proved deleterious to sheep 

 feeding on it in Algeria, and has only been used by man in 

 extreme need. This Lichen-manna has fallen in the form 

 of rain, or has been found suddenly covering tracts of coun- 

 try in Persia, the steppes of Tartary, the countries about the 

 Altai and Caucasus, near Sebastopol and other parts of the 

 Crimea, on Ararat, near Damascus, in Algeria, and in the 

 African Sahara. As an illustration of the circumstances 

 under which this manna-rain is said to fall, Anchercloi states 

 that in 1829, during a war between Russia and Persia, a 

 large tract of country round a town on the south-west shore 



