Spore Shedding Vascular Plants

Psilotum

Lycopodium

Equisetum

Psilotum nudum (whisk fern)

http://imagenes.infojardin.com/sube/images/cqs1194212302m.jpg

Psilotum nudum (whisk fern)

Psilotum has a stem doing virtually all the photosynthesis, with dichotomous branching, enations without vascular tissue, and yellow synangia in the axils of the enations.

Below ground, the stem is not photosynthetic but the epidermis forms rhizoids for anchorage.

The plant thus lacks roots and leaves with underground stem (rhizome) doing the anchorage functions.

Psilotum stem cross section

epidermis cutin guard cells

PSN cortex

lignified cortex

respiring cortex

phloem

metaxylem

protoxylem

radial exarch triarch actinostele

haplosteles

siphonostele

eustele

solenostele dictyostele

atactostele

leaf gap

leaf trace

cortexcortex phloem

xylem

cortexcortex phloem

xylem pithpith

dicot stem

monocot stem

Protosteles:actinostele plectostele

Siphonosteles:

http://sols.unlv.edu/Schulte/Anatomy/Stems/PsilotumWhole.jpg

Psilotum stem specimen more than triarch

http://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/Psilotum_nudum_Rhizome.jpg/800px-Psilotum_nudum_Rhizome.jpg

Psilotum rhizomes with rhizoids

Psilotum rhizome cross-section

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Psilotum stem demonstrates dichotomous branching, enations (no vascular tissue) and two of the three sporangia in a single synangium

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Psilotum sporangium (a three-parted synangium)

This specimen has shed its spores into the wind and so the sterile jackets are empty.

At the bottom of the view is a partial stem cross-section showing: epidermis, cortex and a portion of the vascular cylinder.

http://www.siu.edu/~perspect/01_sp/pics/psilotum.jpg

http://kentsimmons.uwinnipeg.ca/2153/Psilotum_gametophyte.jpg

http://kentsimmons.uwinnipeg.ca/2153/psilotAnthLowMag.jpg

http://kentsimmons.uwinnipeg.ca/2153/psilotoArchigonium.jpg

Psilotum gametophyte tissues all haploid

archegonium

antheridia

Psilotum gametophyte (SE to NW) and sporophyte (Y-shape)

2N rhizome

2N rhizoid

1N gametophyte

1N rhizoid

1N antheridium

The photo is flipped and cropped. Some versions of Powerpoint may fail to retain this making the labels erroneous!

RhyniaCooksonia

Earliest Land Plants

from the

Early Devonian