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Chapter 20: Nonvascular Plants: Mosses, Liverworts, and Hornworts…
Chapter 20: Nonvascular Plants: Mosses, Liverworts, and Hornworts
Concepts
history of true plants
origin from green algae
their adaptation to terrestrial habitats
development of vascular tissues xylem and phloem
origin of seeds
leaves
woody growth
plants divided into
nonvascular plants
called bryophytes
vascular cryptogams
have vascular tissue but not seeds
spermatophytes
have both vascular tissue and seeds
Characters of Nonvascular Plants
mosses
liverworts
relatively unfamiliar
even to most botanists
important understand clearly what
nonvascular plants are not
Tillandsia usneoides
not true moss
several types of lichens
Alectoria
Bryonia
Usnea
"reindeer moss"
Classification of Nonvascular Plants
three distinct divisions
liverworts
#
division Hepatophyta
mosses
#
division Bryophyta
hornworts
#
division Anthocerotophyta
Division Bryophyta: Mosses
The Gametophyte Generation
mosses
occurs in all parts of the world & in almost every environment
ubiquitous
gametophores
leafy stems
many moss plants grow close together
tightly appresses&forming dense mounds
Grimmia Pohlia
hydroids
primarily the family polytrichaceae
innermost cortex is composed of cells
conduct water&dissolved minerals
The Sporophyte Generation
seta
between the foot and sporangium is a narrow stalk
plural
setae
calyptra
apex of the sporangium in many species is covered
Metabolism and Ecology
small size and lack of conducting tissues are two critical factors
Division Hepatophyta: Liverworts
The Gametophyte Generation
leafy liverworts
orders Jungermanniales&Haplomitriales
greatly resembles that of a moss
thin leaves on a slender stem
thallose liverworts
thallus
plural
thalli
body without roots
no stems
no leaves
archegoniophores
stalked
apex is a set of radiating fingers that project outward
droop downward
antheridiophore
male gametophores of
Marchantia
Produce an umbrella-shaped outgrowth
The Sporophyte Generation
elasters
within the sporangium
some cells do not undergo meiosis but rather differentiate
single
elongate cells with spring-shaped walls
liverworts
small plants that have ab alternation of heteromorphic generations
Division Anthocerotophyta: Hornworts
The Gametophyte Generation
always thin
at least along the edges
few as three or four protonema cells are produced before the gametophyte phase is established in most species
The Sporophyte Generation
similar between sporophytes of hornworts&those of mosses or liverworts are not easy to find
hornworts
group of small
inconspicuous thalloid plants that grow on moist oil
hidden by grasses&other herbs
