138 
OF THE LICHENS. 
any other form of plant, those are the most instructive 
examples in which the organs of fructification are well 
displayed. As regards the Lichens, indeed, the presence of 
the fruit is indispensable. 
Investigation into their minute structure is accomplished, 
as in the case of the Fungi, by means of thin sections, cut 
through both frond and receptacle. 
