MICROSCOPIC OBJECTS. 45 



Fig. 89. Transverse Section of the Apothecia of a Lichen 

 (Parmelia parietina), x 200. 



It will be seen from this drawing that, although unlike in 

 their general outward appearance. Lichens much resemble the 

 Fungi in many of their organs. The frond, or, as it is called 

 in this case, the thallus, is composed of four parts, which the 

 drawing represents, the top consisting of a thin layer of the 

 coloration- cells ; next to this are the sacs or thecae, containing 

 the spores, and next to these are the gonidia or globular 

 bodies. These bodies appear to answer many of the purposes 

 of the buds of the higher flowering plants, and are, perhaps, 

 the most useful in its propagation. Next to these are the 

 filaments, some of which answer the purpose of roots; and 

 amidst the upper layers the gonidia are produced. 



A section of the apothecia should be cut with a fine scalpel, 

 soaked in alcohol for a minute, and then taken out and dried 

 under pressure, and mounted in balsam as usual, but without 

 heat. 



Fig. 90. Transverse Section of a Fungus, so-called Scarlet 

 Cup-Moss (Peziza coccinea), x 100. 



The drawing of this Fungus has been taken to show the 

 difference between the parts and those of a section of a 

 Lichen as represented in the preceding figure. The gonidia 

 are wanting, and the coloration-cells, instead of being only a 

 superficial layer, as in the section of the Parmelia, are mixed 

 with the asci. Beneath these is the mycelium, consisting, in 

 this case, of a number of fine felted filaments, producing a 

 leathery kind of thallus (mycelium) . It will be noticed, from 

 these slight descriptions, that in their organic parts Lichens 

 are not unlike the Fungi. 



Sections may be treated in the same manner, and mounted 

 in balsam, although in many cases I prefer fluid. 



