14 



divides Lichens into six classes: (1) Archilichenes, with bright 

 green gonidia ; (2) Sclerolichenes, with bright green or red gonidia, 

 concatenate ; (3, 4, 6) Phycolichenes, Glaeolichenes, Byssolichenes, 

 with various kinds of blueish-green gonidia (goniraia) ; and (5) 

 Nematolichenes, with conferva-like gonidia. But this matter is 

 hardly one for the beginner. Some lichens possess both gonidia 

 and gonimia. There are also dark-colored gonidia, which have been 

 called Melanogonidia. 



The Apothedum. 



We now come to the Apothecium, with its contents, the most im- 

 portant organ of the Lichen. The Apothecia are easily recognized 

 by the naked eye as variously colored disks on the thallus, yellow, 

 brown, or black, or as more minute globose bodies, with a pore 

 (ostiole) at the top. Occasionally they are immersed in the thallus, 

 or even rarely included in it. They are sometimes scattered over 

 the surface of the thallus, sometimes confined to its borders, some- 

 times at the tips of the branches, or of a thalline stalk (Podetium) 

 and sometimes prolonged downward into a stem (Stipe.) They are 

 divided into two series : (1) Gymnocarpous, with open fruit, scutel- 

 laeform, patellaeform, lirellate, or goblet-shaped (crateriform) ; (2) 

 Angiocarpous, with closed fruit (Pyrenocarpous) ; and these series 

 are divided into five tribes, of which four belong to the first series, 

 viz. : (1) Parmeliacei, (2) Lecideacei, (3) Graphidacei, (4) Cali- 

 ciacei, (5) Verrucariacei. The definitions of these tribes will be 

 found in the summary of the system, in the last chapter, so that it 

 is not necessary to repeat them here. But the first thing for the 

 Lichen student to do is to recognize to which tribe a lichen belongs, 

 by observation of the character of the fruit ; then, to ascertain the 

 genus by the combined observation of the Thallus, the Apothecia, 

 and the Spores ; and lastly to determine the species by comparison 

 with published descriptions or with authentic specimens. 



The most general division of the Apothecia is into (1) the Lecano- 

 rine, those having a disk enclosed in a margin, (exciple) formed from 

 the thallus ; (2) the Lecideine, in which the margin is not formed 

 from the thallus, and is called a proper exciple, as distinguished from 

 the thalline ; and (3) the nucleiform, or Pyrenocarpous, belonging to 

 the fifth Tribe. The exciples in Tribes 3 and 4 are like those in Tribe 

 2. When the proper exciple is not coal black (carbonaceous) but col- 



