56 THE WONDERS OF VEGETATION. 



not of equally good quality, cannot be as easily purified, 

 and leaves an unpleasant resinous matter behind in- 

 stead of wax ; still others, like the Hura Crepitans, 

 are actually poisonous, and the sap is employed to 

 poison the waters of rivers for the purpose of killing 

 the fish. 



THE MANNA-TREE. 



During the intense heat of the month of August, 

 when the sap is abundant, this tree furnishes a nutri- 

 tive substance of slightly bitter taste. It is a natural 

 secretion of the plant, and has procured for it the 

 name which recalls the miraculous food of the Israel- 

 ites in the desert. Manna is a liquid substance as 

 clear as water, and flows from the tree, if about the 

 middle of August an incision is made in the bark. 

 Generally the tirst cut is made near the foot of the 

 tree ; and each day a new incision is added two inches 

 above the last and so on up to the lower' branches. 

 These cuts, generally made with a pruning-knife or 

 carpenter's chisel, are usually two inches in length 

 and half an inch deep. 



At first the sap flows abundantly, like a liquid 

 stream ; at the end of a month it becomes thicker 

 and flows less freely. The rainy season interrupts it 

 altogether, and towards the end of September the 

 heat of the day is no longer sufficiently powerful to 

 make the sap rise, which gradually recedes to the 

 lowest parts of the tree. 



The manna gradually loses its slightly bitter 

 taste which it had when taken from the tree ; the 



