336 PRACTICAL COURSE IN BOTANY 
Observe a tiny dot near the center of the rhomboidal areas 
into which the epidermis is divided and compare it with 
your drawings of stomata (181, 183). 
What would you judge that these dots 
are ‘for? While differing in structure 
Se from the stomata of leaves, they serve 
Fic. 477.— A portion 
of the upper epidermis the same purposes and may be regarded 
of marchantia, magni- as 4 more rudimentary form of the same 
fied, showing rhomboidal 
plates with a stoma in Organ. 
eek 386. Rhizoids. — Wash the dirt from 
the under side of a thallus and examine with a lens; how 
does it differ from the upper surface? Do you see anything 
like roots? Place one in a drop of water under the micro- 
scope. Compare with similar organs found on the lichen 
(379). What are they? Would rhizoids be of any use on 
the upper side? stomata on the under side? 
387. Gemmez.— Look along the upper surface for little 
saucer-shaped (in lunularia, crescent-shaped) cupules (g, g, 
Fig. 476). Notice their shape and position, whether on a 
midrib or near the margin. Examine the contents with 
a lens and see if youcan tell what they are. These little 
bodies, called gemme, are of the nature of buds, by which 
the plant propagates itself vegetatively somewhat as the 
onion and the tiger lily do by means of bulblets. Sow some 
of the gemmez on moist sand, cover them with a tumbler 
to prevent evaporation, and watch them develop the thalloid 
structure. 
388. The fruiting receptacles.— Procure, if possible, 
thalli with upright pedicels bearing flattened enlargements 
at the top (Figs. 475, 476). These are thallus branches 
modified into receptacles containing the reproductive organs, 
which, in marchantia, are dicecious, the two kinds growing 
on separate thalli. Notice their difference in shape, one 
kind being slightly lobed or scalloped, the other rayed like 
the spokes of a wheel. The first kind are known as antherid- 
tal, or male, receptacles; the second as archegonial, or female. 
