SECT. IV. LEAF-STALK AND LEAF. 275 



lar is that the fibres are not only subdivided 

 into a variety of ramifications forming a fine net- 

 work, but that the net-work is double (PL VIIL 

 Fig. 3.), consisting of two layers, the one corre- 

 sponding to the upper, and the other to the under 

 surface of the leaf. Hollman detected and sepa- 

 rated them in the leaf of the Pear-tree,* and 

 Linnaeus in the leaf both of the Pear and Apple- 

 tree. He even discovered their points of union, 

 and remarked that the net- work corresponding to 

 the under surface was much less firm and com- 

 pact in its texture than that corresponding to the 

 upper surface. Hedwig discovered two layers, even And 

 in the minute and tender leaf of Sphagnum palustre^ S f 

 and affirms that he found, in the leaves of the Pear la y ers 

 and Orange-trees, three layers of net-work,-^ which 

 I have not indeed been able to detect in the 

 former. But no language is able to convey an ade- 

 quate idea of the delicacy and intricacy of the 

 web. It must be inspected as it exists in the con- 

 texture, or rather in the decay of the leaf, whole 

 leaves being often found reduced to a skeleton of 

 fibres in the winter or spring, lying at the roots of 

 trees in situations where they have not been dispers. 

 ed by the wind. But if they are not to be found 

 ready prepared as in this case, the dissector must 

 have recourse to maceration. 



* Phil. Trans. 174L, f Fund. Hist. Nat. Muse. chap. Y. 

 T2 



