CARPOSPOREM. 



31^ 



a fact first observed by Famintzin and Baranetzky, but incorrectly explained. It is to 

 Schwendener's knowledge of the facts, the result of researches extending over many 

 years, that the correct interpretation is due in these cases of the relationship borne by the 

 Lichen-forming Fungus to the gonidia, i. e. to the Alga which it attacks\ 



After these preliminary remarks the following description will be intelligible to the 

 beginner. It is transferred, with but slight alterations, from the first edition of this 

 book. We will consider first the Lichen as a whole, as it comes under observation, the 

 nourishing Alga being distinguished as an elemental form of the thallus under the name 

 Gonidia ; and we will afterwards discuss the question of their algal nature more in detail. 



The Thallus of Lichens is commonly developed in the form of incrustations which 

 cover stones and the bark of trees, or penetrate between the lamellae of the epidermis of 

 woody plants, and then expose only the fructifications above the surface. These Crus- 

 taceous Lichens, as they are termed, have become so completely united in their growth 

 to their substratum, at least on the under side, that they cannot be detached completely 

 from it without injury to the thallus (Fig. 210, A^ B,C). The crustaceous Lichen-thallus 



Fig. 211.— a piece of the foliaceous thallus o{Pei- 

 tigera horizonialis ; a the apothecia ; r the rhizines 

 (natural size). 



Fig. 2to. — A, B Graphis elegans, a crustaceous Lichen 

 growing on the bark of the Holly ; A natural size,'/? slightly 

 magnified ; C Pertusaria Wtdfeiii, another crustaceous 

 Lichen (slightly magnified) 



Fig. ■2\'2.—CoUe7na pidposictn, a gelatinous Lichen 

 (slightly magnified). 



passes over, through various gradations, into that of the Foliaceous Lichens ; the latter 

 forms flake-like expansions often curled, which can be completely detached from the 

 ground, stones, moss, bark, &c. which support them, since they are attached to it only 

 in places by a few organs of attachment, the Rhi%ines. The foliaceous thallus often 

 attains considerable dimensions, in the large species of Peltigera and Sticta as much as 

 a foot in diameter, and from ^ to i mm. in thickness, and then generally assumes a 

 circular form; at the growing margin it forms rounded indented lobes (Fig. 211 and 

 Fig. 213, 5). A third form of the Lichen-thallus, also united with the previous one by 

 transitional forms, is shown in the Fruticose Lichens, which are attached only at one spot 

 and with a narrow base, and rise from it in the form of small much-branched shrubs. 

 The branches of the thallus are either flat and ligulate, like ths lobes of many foliaceous 

 Lichens, or slender and cylindrical (Fig. 213, A). In Cladonia and Stereocaulon we have not 

 so much a transition from the foliaceous to the fruticose thallus as a combination of the 



* A few additional historical notes will be found at the end of this section. 



