170 MICHIGAN ACADEMY OF SCIENCE. 



THE LICHEN GENUS PHYSCIA. 



E, E. BOGUE^ AGRICULTURAL COLLEGE. 



The person who begins the collection of lichens in this region will find 

 Physcia stellaris among his first ten. 



At first sight lichens may seem to be in a bad mix up, but we do not 

 proceed far, provided we get started on the right track, before we dis- 

 cover that like all other organic bodies there is something of a natural 

 sequence. 



The arrangement of the higher groups of lichens is now fairly settled 

 and will jirobably remain about as they are until some one thinks they 

 need an overhauling when he will turn the present arrangement topsy 

 turvey, and then we shall need some new guide posts along the lichen 

 road. 



According to Tuckermau, our lichens are placed in two series, which 

 are named much like the series of flowering plants, viz., Gymnocarpi or 

 naked fruit and Angiocarpi or covered fruit. The (xymnocarpi are further 

 divided into four tribes, sixteen families and sixty-two genera. The 

 Angiocarpi, into one tribe, two families and ten genera. Physcia is the 

 fourth genus of the second family of the first tribe of Gymnocarpi and 

 is related to Parmelia on the one hand and Pyxine on the other. 



In lichens the fruiting body is called an apothecium, in certain groups 

 of fungi perithecium. As in other forms of vegetable growth, the fruit 

 is the thing we need for classification in most cases. The species of 

 Physcia generally fruit freely but there are some common species whose 

 fruit I have never seen during twelve vears of studv and observation of 

 lichens. 



The fruit is borne in little receptacles that in build are like miniature 

 patterns of the thick, heavy saucers that a(Com])any the cups in which 

 we are served cofi'ee at the short-order restaurant. These apothecia are 

 modified developments of the lichen thallus or the part that forms the 

 most conspicuous part of the plant. The species of Physcia may be 

 found on the bark of both live and dead trees, dead wood, stone and other 

 substances. The thallus is frequently broken up into small pieces, es- 

 pecially in the older portions, and is usually represented by radial, broken, 

 branched bands or- may be in scattering small pieces that have no definite 

 ari-angement. The thallus is for the most part some shade of green above 

 and sometimes white beneath. Little black fibrils are usually present 

 beneath. The spores are ellipsoid, brown, and in our native sj)ecies show 

 only one division. Tuckerman enumerates thirty species and varieties 

 in his ''Synopsis of N. A. Lichens." Of these I have sixteen in my collec- 

 tion and no especial attention has been given to this genus. Thei-e is a 

 larger number of some other genera. 



Fhij.scia speciosa. — This will be found with a rather com])act leathery 

 thallus on bark, stones and among moss in woods. It is what the horti- 

 culturist would call a shy bearer, for T have it from seven difterent locali 

 ties by four difi'erent collectors and not a single fruit is to be found. 



