180 PRACTICAL MICROSCOPY. 



leaves of orchids, where it is easily found, underneath the 

 cuticle, after maceration. Woody tissue, often the chief 

 component of certain plants used in the arts, is composed 

 of fibro-vascular vessels aggregated in bundles, as in flax 

 for instance ; and the same may be said of jute, china- 

 grass, and many other products. These fibres may be 

 examined by macerating in water, during which a fermen- 

 tation sets in, and the fibrous bundles consequently split 

 up ; the same effect may be produced by boiling with 

 dilute caustic soda solution. 



Spiral fibres also form interesting objects for study. 

 They occur sometimes in cells alone, and at others in con- 

 junction with what have been styled bordered pores, as in 

 the yew and araucaria, while the pores are found alone in 

 the pine. Most woods, when in thin shavings, are easily 

 decomposed by boiling with dilute nitric acid, when the 

 fibres can be pulled asunder, or by boiling with caustic 

 soda solution under pressure. 



Spiral vessels are even more interesting than any of the 

 foregoing, and easily procured. From the stem of the leek 

 they are separated with ease, while from the petiole of the 

 common garden rhubarb they can be obtained in plenty by 

 searching in a pot of this preserve. 



Perhaps of all exercises the complete dissection of a moss 

 is the best for botanical students ; the various parts 

 mounted on an ordinary slip under a three-quarter thin 

 glass cover are at once a type slide and an object of 

 beauty. 



Scalariform vessels are to be met with in the roots of 

 ferns. The Pteris aquilina perhaps displays them as well 

 as any other plant ; but it is a moot point whether they are 

 better seen by the examination of a dissected portion, 

 rather than a section made in a diagonal direction. It is 

 true that much can be made out from sections of the 



