TYPES OF CRYPTOGAMS; THALLOPHYTES 271 
329. The Fruit. — Look for small lance-shaped disks seated upon 
the thallus. Note the approximate sizes and color within and 
without. These disks are called apothecia. Note the very minute 
black specks (spermogones) which are scattered in the surface of 
the thallus. Pick one from the thallus, with as little of the thallus 
as possible, and examine under high power. It may be macerated 
in a drop of potash solution and crushed under the cover-glass. If 
the contents are not easily 
defined, they may then be 
made more opaque by a drop 
of acetic acid or a stain. The 
minute colorless bodies con- 
tained in the spermogones are 
(= 
Mia 
| 
\ 
\ 
Fig, 198, — A Lichen (Xanthoria). Fie. 199.— A Lichen (Usnea). 
(Natural size.) (Natural size.) 
called spermatia. Their office in Physcia is obscure, but in a few 
lichens they are thought to unite with a trichogyne cell, as in the red 
alge.1 Note the minute, powdery masses (soredia) on the surface 
of the thallus. Macerate if necessary under the cover-glass and 
examine under a high power. Compare with the structure of the 
thallus as seen in cross-section. (See next paragraph.) These soredia 
easily become detached and develop into new plants. 
Prepare for sectioning by imbedding a small portion of the 
thallus with an apothecium in a piece of pith or by any suitable 
device for sectioning, and cut thin sections of thallus and fruit. 
‘1This, however, is doubtful. See Strasburger, Noll, Schenk, and 
Schimper’s Text-Book of Botany, p. 380. : 
