TYPES OF CRYPTOGAMS ; BRYOPHYTES 279 
337. Internal Structure. —Cut thin cross-sections of the thallus 
in the same way as for Physcia, making some pass through the cir- 
Fic. 203. — Section through Anther- 
idial Receptacle of Marchantia. 
(Magnified.) 
a, antheridium. 
cular dots mentioned above. Exam- 
ine under a high power and note the 
different kinds and layers of cells 
composing the thallus. Note the 
character of the cells forming the 
upper and lower surfaces. Describe 
the cells which are next above those 
of the lower epidermis, their shape, 
color of contents, approximate num- 
ber of horizontal rows. Have they 
any evident intercellular spaces? Find 
cells connecting these with the upper 
epidermis and constituting the net- 
work of lines seen on the surface of 
the thallus. Note the air cavity 
bounded by these lines ial the loose cells which occupy it in part. 
What is the color of their contents? How are they attached, and 
how arranged? Can you discover any 
opening through the epidermis? If so, 
describe it. 
Make drawings to illustrate the details 
of structure observed. 
338. Gemmz. — Look for a thallus 
AZ 
bearing little green cups formed of its 
own substance. Describe the contents 
of the cup. The bodies are called gemme. 
They originate by vegetative growth alone 
and when detached may grow into new 
plants. 
339. Fruiting Organs, — Look for thalli 
bearing stalks with umbrella-like expan- 
sions. The umbrellas are of two kinds, 
one disk-like with crenate points (how 
FiG. 204. — Sectional View of 
an Antheridium of Mar- 
chantia. 
a, antheridium ; az, anthero- 
zoids, Xx 700. 
many ?) and the other has rays (how many?) elongated and curving 
downward. Is there any difference in the height of the two kinds? 
