15 



ored or blackening, it is called Biatorine. In many species of the 

 first Tribe the thalline exciple is often obscured, or depressed, when 

 the Apothecium appears Biatorine, and it may not always be easy 

 to determine at first sight to which tribe the plant belongs. In this 

 tribe there is also often a proper exciple enclosed in the thalline. 

 Such a composite exciple is called Zeoriue. Some apothecia become 

 tubercular and appear to have no margin, and in some genera of the 

 third Tribe the exciple is altogether deficient. Sometimes there are 

 numerous apothecia situated on a common receptacle called a 

 Stroma ; and some Lecideine apothecia are inclosed in a pseudo- 

 thalline, or as it is called Thalloid exciple, more of the nature of a 

 Stroma. The external covering of the Apothecia of the fifth Tribe 

 is called a Perithecium, and within it is usually an inner envelope, 

 the Amphithecium, within which is the globular nucleus. In one 

 genus of the first Tribe, Pertusaria, many of the apothecia have one 

 to six pores, but the general character of the fruit is that of ^e 

 Tribe. Undeveloped Apothecia of other members of this tribe have 

 sometimes the appearance of those of the fifth Tribe. 



Now let us examine the Apothecium internally as we already have 

 the Thallus, by making a thin section of that, for example, of a Par- 

 melia. Before making the section, by the way, the plant should be 

 saturated with water, as Lichens swell when filled with water, es- 

 specially some of the Collemacei. Such a section will sliow us 

 (looking from above) (1) a thin epithecium, sometimes granular 

 above ; (2) around the borders the thalline exciple containing Go- 

 nidia ; (3) included within this the Hymenium, containing the Par- 

 aphyses and the Thekes ; and (4) below this, a colorless or brownish 

 or black portion, the Hypothecium. The Paraphyses are elongated 

 cells or filaments, proceeding from the medullary layer, arranged 

 perpendicularly to the plane of the section, sometimes closely agglu- 

 tinated by the hymenial gelatine, sometimes lax, sometimes obsolete 

 or hardly perceptible, as in the nucleus of most apothecia of the fifth 

 Tribe, and sometimes deficient; sometimes jointed, often swollen 

 (clavate) at the tips. The Hymenium is now colorless, now brown 

 or black, sometimes bluish. 



Between the Paraphyses are the Thekes, containing the Spores. 

 The Thekes are of various form aud size. In form they are mostly 

 club-shaped, (clavate,) but now cylindrical, acuminate, pear-shaped, 



