CBTPT0GA2BXA.. 119 



also to supply descriptions of the species new to Germany or to sci- 

 ence which have occurred since the publication of; he latter work. 

 .Nylandek. — Synopsis niethodica Lichenum omnium hueusque uugnito- 

 rum praemissa introductiune lingua gallica trad at a ; ocripsit William 

 Nylauder. 1st fascicle, Paris, 1858. 2nd iascicle, Paris, 1860. 



The first fascicle consists of two parts — one general, the other 

 descriptive. The first part, written in French, contains an account 

 of the organisation, clarification, and distribution of Lichens. The 

 eleven chapters of which it is composed, relate to the following mat- 

 ters : — 



1. Definition of Lichens. Lichens (says M. Tsylander) are cel- 

 lular plants; their fructification is borne upon a thallus furnished 

 with gonidia, and has ahymenium containing an amyloid gelatinous 

 substance. They are characterized by a slow and intermittent 

 growth, dependent upon the state of humidity of the atmosphere ; 

 and, for the most part, they derive their nourishment from the at- 

 mosphere. They differ further from fungi in the fact of their hyme- 

 nium usually assuming a blue or vinous red colour under iodine. 



2. The constituent parts of Lichens — viz., the iJicdlus, or vegeta- 

 tive part; the apotheeia, or thccasporous fruit; the spermogonia, 

 which have been supposed to represent male organs; and iuepycnidia, 

 the nature of which is obscure. 



3. The thallus. This assumes four principal forms — the folia- 

 ceous, the fruticulose, the crustaceous, and the hypophleodal thallus, 

 which lies concealed under the epidermis of trees, or between the 

 fibres of the wood. The thallus is usually stratified, more rarely 

 formed of a homogeneous tissue. The stratified thallus has three or 

 four layers — the cortical, the g'midial, the medullary, and frequently 

 a hypothalline layer, which sometimes forms a hypothallus, and 

 sometimes rootlets or root-like fibrils. Homogeneous thalli are only 

 met with in the lower Lichens. 



4. Apothecia. These form sometimes a disc, sometimes a rounded 

 nucleus. They consist of the combination of three layers, viz., the hypo- 

 thecium,orperithecium, or conceptacle, which corresponds to the hypo- 

 thallus ; 2, the thecium, which is analogous to the gonidio-medullary 

 layer of the thallus, and which is formed of a mass of paraphyses and 

 thecse ; 3, the epithecium, corresponding to the epithallus, or cortex ; 

 4, the spermogonia ; these are generally very small, round, or ob- 

 long nucleiform organisms, sometimes lodged in particular tubercles, 

 but more frequently immersed in the superficial layers of the thal- 

 lus, and having the appearance of small papillary elevations, or sim- 

 ple ostioles, sometimes black or brownish, sometimes of the same 

 colour as the thallus itself. They are composed of a conceptacle, 

 quite analogous to that of the apothecia — of sterigmata, which are 

 cellules with delicate walls, usually elongated, which grow on the 

 internal surface of the conceptacle, and which are erect and simple, 

 or slightly branched — and, lastly, of spermatia, borne by the sterig- 

 mata, and which are very minute acicular, ellipsoid, or oblong bodies, 



