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)