130 MICROSCOPIC OBJECTS. 



cuticle silica or flint. This is especially the case with 

 Graminacese. In wheat and barley straw the quantity is 

 smaU ; in the bamboo it is much larger, and a siliceous 

 body, containing a little lime and vegetable matter called 

 tahasheer, so remarkable from its slight refractive power, 

 is secreted in the joints of that cane. 



The polishing quality of the rush arises from this 

 deposit. — To prepare these bodies for the microscope, it 

 is necessary to make thin slices of the cuticle ; and if 

 hey are not sufficiently transparent, immerse them in 

 Canada balsd-m between two shps of glass. The mag- 

 nifying power required for these examinations varies 

 greatly according to the size of the particles deposited, 

 and therefore cannot be stated with advantage. 



