Early Plants

Characteristics

Psilotum

Lycopodium

Selaginella

Ancient Lycopods

Equisetum

Ferns


Psilophyta:

Only 2 living genera still exist - Psilotum and Tmesipteris

Characteristics of Psilotum: No true leaves or roots - basic organ is a true stem with rhizomes or underground stem branching off. (By true we mean containing an actual vascular system)

a. A simple design: dichotomous branching ( di = 2)..each fork branches off to form 2 new branches.

b. Enations: tiny green flattened protuberances with no veins so they are not considered a true leaf

c. Rhizoids originating on the rhizomes with mychorrhizeal ( fungal symbioants) associations

d. A cross section reveals the production of : true xylem & phloem and stomata

e. Plants are located in tropical and subtropical USA and Hawaii

f. Economic uses- laxative (perhaps meaning it is so nasty that you gut will evict as soon as possible) , its' biochemistry needs study.

Life cycle: Please note:

a. Transition of main life stage to the sporophytic stage and reduction of the gametophytic stage.

b. The gametophyte is only 1/4" long, bisexual and is saprobic- it gains its energy through an association with a fungus ( a endomycorrhizal)