270 ESSENTIALS OF BOTANY 
347. Minute Structure of the Sporophyte. — Pick out from old re- 
ceptacles some of the full-grown sporophytes, mount, and examine 
with m.p. Note: 
(a) The foot (which was imbedded in the receptacle), the slender 
stalk, and the enlarged spore-case. Draw. 
(0) Spores. 
(c) laters, spirally-marked cells which assist in scattering the 
spores. Draw (0) and (c) under h.p. 
348. Discussion. — Marchantia is far more highly spe- 
cialized for utilizing the raw materials of plant food than 
are any of the alge or fungi studied in previous sections. 
Its thallus has a well-defined 
epidermis, especially firm on 
the upper surface to pre- 
vent undue loss of water. 
The rhizoids are efficient in 
absorbing water containing 
nutrient substances from 
the earth. The air-cham- 
bers beneath the upper sur- 
face of the thallus, with 
their hair-like chlorophyll 
Fic. 195. Frullania, a Leafy Liver apparatus, are admirably 
wort, growing on maple bark. adapted for photosynthesis. 
scant Asexual reproduction is 
well attained by the separation of young branches (set 
free by the dying of the older parts) and by the numer- 
ous buds. 
The sexual reproduction is of a complicated character, 
brought about by the conjugation of unlike gametes. 
349. Alternation of Generations. —In the reproduction 
of Marchantia for the first time in the studies of spore- 
plants outlined in Chapters xx11I-xxvu, the student fully 
