158 MORPHOLOGY. 



attachment (rhizince). For the most part the thallus foliaceus is 

 more or less closely appressed to the supporting surface, sometimes 

 only fastened at the middle point by a small adhering disc (as, for 

 instance, in Urnbilicaria) ; at others it rises freely, and then appears 

 in flat ramifying forms, which always admit of being distinguished 

 from the succeeding form by the inequality of their two surfaces. 



Finally, in the highest forms the cellular mass rises and forms 

 multifariously ramifying bands or threads of greater or lesser thick- 

 ness (thallus fruticulosus). 



We know but little as yet of the law of development of Lichens. 

 Hitherto, Meyer* and Wallroth| are the only ones who have given us 

 any information on the subject ; yet both were as deficient in funda- 

 mental physiological information to know what was requisite, as in good 

 microscopes, &c., to see things worthy of being noticed. Meyer has 

 clearly and fully explained all that could be seen with the naked eye, 

 whilst "Wallroth has rendered his work wholly unendurable by the use 

 of a terminology as superfluous as it is disgustingly barbarous. 



The structure of the forms in Lichens is on the whole very simple. As 

 they almost all grow uniformly from one point of the spore in all direc- 

 tions, and are besides generally attached to the supporting surface, the 

 most general is the round outline, modified by the form of the surface on 

 which they grow, and by the specific structure of the lobes. In some, as, 

 for instance, in those nuclear Fungi which I include under the same head 

 and Helvellacece, and also in many true Lichens, especially in the pul- 

 verulent Lichens, or as, for instance, in Coniot/ialami, and some columel- 

 lar Lichens, the plant is so perishable that we scarcely find anything 

 beyond naked sporocarps. In some^ as in the Graphidece, &c., the plant, 

 similarly to what is the case in most Pyrenomycetes, expands itself 

 within those parts of plants (mostly bark) which serve as a basis to 

 it, and subsequently, after the destruction of the covering, nothing 

 appears but the naked sporocarp, or sometimes, but rarely, also the 

 plant itself. It is only in a very few cases that the plant rises stem-like 

 and free from the base, either by the erection of the lobes, as inEvernia, 

 Borrera, &c., or by some real difference of development, where the plant 

 developes linearly upwards instead of laterally and superficially ; thus, 

 consequently, exhibiting the same surface as it had previously done 

 while recumbent. The word thallus is superfluous in the case of such 

 a plant. 



88. The development of the spores is very uniform for all cases 

 included within the limits of this family. At wholly indefinite 

 parts of the surface of the plant, there is formed a semi-circular 

 channel-shaped, or more or less spherical or cylindrically closed 

 layer of delicate walled, closely packed, roundish cells, which 

 sometimes appear coloured, as in Lecidea sanguined (when form- 

 ing a rim round the developed sporocarp, named excipulum pro- 

 priwni) ; and on the inner surface of this layer is a second, composed 

 of thin filiform cells (paraphyses, Saftfaden), placed vertically 

 upon the preceding layer (Lamina proligera Auct.). By degrees, 



* The Development, Metamorphosis, and Propagation of Lichens. Gottingen, 1825. 

 j- Natural History of Lichens. Frankfort, 1825-27. 



