ANATOMICAL STRUCTURE OF LEAVES. 93 



minute as to be individually invisible to the naked eye, 

 but giving- a red tinge to the leaf. Such glands are 

 found nowhere except upon the upper surface of the 

 leaf, in the neighbourhood of the delicate seat of 

 irritabilitv. It is in vain that you stimulate the teeth 

 of the margin, the back of the blade, or its stalk ; 

 in none of these parts is there a trace of irritability ; 

 and in none of these parts is there a trace of the 

 glands. It is not, therefore, improbable that these 

 glands are either in some way connected with the irri- 

 tability, although it is not they through which the 

 shock is first communicated to the leaf, or, as Mr. 

 Curtis supposes, are intended to absorb the nutriment 

 afforded to the leaf by the decay of the insects en- 

 trapped in it. 



Let us be a little more particular in the examina- 

 tion of the Dionsea leaf ; for it will not only give vou 

 instruction in respect to the plant actually before vou, 

 but vriW afibrd an insight into the general nature of 

 the anatomy of all leaves. 



With an exceedingly sharp, thin-bladed knife, 

 obtain a thin slice of a leaf, in the direction of its 

 veins (as from b to e in Plate XXXIV. Jig. 1.), so as 

 to shew its whole thickness. Place it under a good 

 microscope, in water, and by means of the mirror 

 throw light upon the slice from below ; it will then 

 become a transparent object, and you wilL be able to 

 see all that minute, internal organization, which is 

 entirely invisible to the naked eye, and which enables 

 the leaf to breathe, perspire, digest, and perform 

 its other manifold offices. You will also find that a 



