120 BIBLIOGRAPHY. 



constituting (the author considers), with great probability, the male 

 organs of the Lichens. 5, the pycnidia, which Tulasne considers 

 to be supplementary sporiferous organs, which resemble the sper- 

 mogonia in form, in their eoncepiaclcs, and in the mode of insertion 

 of the organs called slylospores, which they produce, but which latter 

 are less numerous than the spermatia, of a much larger size, and 

 capable of germination. 



The seventh chapter contains a recapitulation of the anatomical 

 elements of Lichens ; the eighth chapter treats of their chemical 

 properties and uses; the ninth, of their specific characters; and the 

 tenth, of their classification. 



M. Nylander divides the Lichens into three families : the Col- 

 lemacei, the Myriangiacei, and the Lichenacei. The Collemacei are 

 distinguished by their heavy, dark colour, and by the structure of 

 their thallus, which is rarely cellular, and is usually gelatinous, contain- 

 ing gonimic granules, scattered or in rows. The Myriangiacei com- 

 prise only two species of the genus Myriangium. They resemble the 

 Collemacei in their external form and colour, but in their thalline 

 tissue and thalamial tissue are nearer the Lichenacei: Their spheroidal 

 thecse are always arranged irregularly, and are sometimes superposed 

 in two or three rows. The Lichenacei are divided into six series : 1. 

 theEpiconiodei, in which the spores, when they have escaped from the 

 thecaB, accumulate like powder on the surface of thehymenium ; 2, the 

 Cladoiiiodei, or Lichens with a stipitiform thallus, usually fruticulose, 

 and furnished with squamules or folioles, with lecideine and convex 

 apothecia (apothecia cephaloidea) ; 3, the Ramalodei, or Lichens with a 

 fruticulose thallus, compressed or cylindrical, without squamules, and 

 with fruit generally lecanorine and flat ; 4, the Phyllodei, or Lichens 

 with a foliaceous thallus, and usually lecanorine apothecia, with jointed 

 sterigmata ; 5, the Placodei, or Lichens with a crustaceous thallus 

 and lecanorine lecideine, or lirelliform apothecia ; 6, the Pyrenodece, 

 or Lichens with a peltate thallus or a crustaceous thallus, sometimes 

 without any thallus, with pyrenocarpous apothecia, either immersed 

 in the thallus, or more or less naked. A table of the families, series, 

 tribes, and genera, is added. 



The eleventh chapter treats of the geographical distribution of 

 Lichens. After this follows the systematic portion of the work, 

 written in Latin, containing descriptions and synonyms of species, 

 with indications of their geographical distribution. 



The two fascicles already published include the Collemacei and 

 the Myriangiacei, and the first four series of the Lichenacei, with the 

 exception of the tribes Gyrophorei and Pyxinei, which, with the 

 series Placodei, which includes the tribes Lecanorei, Lecidinei, 

 Xylographidei, and Graphidei, are to be dealt with in the forthcoming 

 concluding parts. 



There are eight plates accompanying the two fascicles already 

 published, giving illustrations of the genera, and of a certain number 

 of species. 



