Botany · Ch 2 — Plant Kingdom
Marchantia
Marchantia
Marchantia (Class Hepaticopsida, Order Marchantiales) grows in cool, moist, shady places; Marchantia polymorpha is the commonest species. Its gametophyte — the actual plant body — is a prostrate, dorsiventral, dichotomously branched thallus. The dorsal surface shows a shallow midrib groove and a pattern of rhomboidal or polygonal outlines that mark the underlying air chambers, plus crescent-shaped gemma cups holding vegetative propagules called gemmae; an apical notch at each branch tip drives growth. The ventral surface bears multicellular scales and two kinds of rhizoids (smooth-walled and pegged) for anchorage and water/mineral uptake. At maturity, the thallus produces erect, stalked reproductive branches — antheridiophores and archegoniophores.
In transverse section the thallus shows three layers: an epidermis (upper layer single-celled and chloroplast-bearing, interrupted by barrel-shaped air pores that open into a single horizontal layer of air chambers whose floor bears simple or branched photosynthetic filaments), a photosynthetic region, and, below it, a storage region of tightly packed parenchyma cells loaded with starch and protein; the lower epidermis carries the rhizoids and scales. …
What this figure shows. (a) A thallus bearing an umbrella-like antheridiophore (male gametophore) on a stalk. (b) A thallus bearing an archegoniophore (female gametophore), which is more deeply lobed/finger-like than the antheridiophore; both arise from a prostrate, dichotomously branched thallus with rhiz …
What this figure shows. A transverse section showing, from top to bottom: an upper epidermis interrupted by barrel-shaped air pores that open into a single layer of air chambers floored by branched photosynthetic filaments; below this, a compact parenchymatous storage region packed with starch and protein; and on the lower (ventral) surface, smooth-walled and pegged rhizoids tog …
What this figure shows. (a) A vertical section of a gemma cup on the thallus surface, containing several disc-shaped gemmae attached by short stalks. (b) One gemma enlarged, showing its two lateral notches (each with a growing point), a central stalk (stipe) and scattered oil cel …
What this figure shows. (a) A longitudinal section of an antheridiophore showing club-shaped antheridia embedded in the photosynthetic tissue on its upper surface. (b) A longitudinal section of an archegoniophore showing flask-shaped archegonia hanging from its lower surface, surrounded by a pro …
What this figure shows. The sporophyte differentiated into a bulbous foot embedded in the gametophyte, a short seta, and a capsule; the capsule is shown packed with haploid spores mixed with thread-like elaters, and the whole sporophyte is enclosed by a protective c …
What this figure shows. A haplo-diplontic life-cycle chart: the dioecious haploid gametophyte forms separate male (antheridiophore) and female (archegoniophore) thalli. Antherozoids from the antheridium fertilize the egg in the archegonium to give a diploid zygote, which develops through an embryo into a sporogonium bearing spore mother cells; these undergo meiosis to give a spore tetrad and free haploid spores, which germinate via a germ tube into a new gametophyte. A separate vegetative loop shows fragmentation, adventit …