104 THE NORTHERN MICROSCOPIST. 
little wart upon the thallus, then it is verrucose. Besides these, 
there are other forms. The structure of the apothecium is the 
most complex part of the plant; and it is beautiful in its arrange- 
ment, as well as efficiently adapted for its purpose of maturing and 
protecting the spores. The apothecium consists of two parts: an 
excipulum and a nucleus, called the hymentum. The excipulum is 
the outer covering, or envelope of the apothecium. It is seen 
encircling, or more or less enclosing the fruit. When it is of the 
same texture and colour as the thallus, it is termed a ¢halline 
excipulum, But when it differs from the thallus, and partakes more 
of the colour of the nucleus, it is a proper excipulum. ‘The 
hymenium, or thalamium, is the centre of the fruit organ, and is 
easily recognised by its colour and gelatinous appearance. It em- 
braces the paraphyses, asci and spores. The paraphyses (6 Fig. 14) 
are long, slender, cylindrical, hyaline cells, or filaments; swollen at the 
apices into the shape of a club, where they are also frequently of a 
dark or pale colour. They grow upright or vertical from a bed of 
cells, known as the Ayfothecium, (4 Fig. 14), and stand like corn ina 
field, only closer together. Their apices are glued into a solid mass, 
and form what is called the efzthecium, or disc of the fruit. The 
direct function of the paraphyses is not clearly understood; but it is, 
without doubt, to subserve the spores. By their agglomeration, 
they retain around the asci, if they do not secrete it, a large quan- 
tity of lichenine, which helps the nourishment of the young 
sporidia. They also hold up the asci in a vertical position, when 
being full of spores, they would otherwise fall down upon the 
hypothecium ; and when the asci and spores are ripe they act as a 
sort of spring upon them, caused by the expansion and contraction 
of damp and dry weather. The spores are thus, by pressure 
expelled into the air, through the disc or epithecium ; when the 
wind wafts them on, to grow in new spheres. The asc or theca, (5 
Fig. 14), are large vesicles or sacs, growing upright among the para- 
physes from the hypothecium. They are in shape oblong, pyriform, 
linear or clavate ; but always tapering off at the base. They are 
closely pressed by the paraphyses, from which they differ by being 
broader and inferior in length. The spores are formed and 
matured in these sacs ; and when ripe, by the lateral pressure of 
the paraphyses, or the internal pressure of the spores, or from 
both, the ascus ruptures at the apex, and the spores are liberated. 
The spore (Gr. sfora, a seed), Fig. 14, is the reproductive germ. It is 
formed in the ascus from a protoplasmic-lichenine matter. When 
mature, it consists of a cell having an inner and outer wall, termed 
respectively, the exdosporium and episporium. It is frequently 
divided by septa into two or more cells. The spores are generally 
eight in number, in each ascus; but some of the larger spored 
forms, as Pertusaria, produce in the spore-sac four, two, and some- 
