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/oo( (which was imbedded in. the receptacle), the slender 

 stalk, and the enlarged spore-case. Draw. 



(ft) Spores. 



(c) Slaters, spirally-marked cells which assist in scattering the 

 spores. Draw (6) 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 algae 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 

 apparatus, are admirably 

 adapted for photosynthesis. 

 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 xxiii-xxvn, the student fully 



ITiG. 195. FruUania, a Leafy Liver- 

 wort, growing on maple bark. 

 (About natural size.) 



