Psilotum does not have true leaves, just small scale-like outgrowths. The other genus in this division/phylum (Tmesipteris) has larger “scales”.

 

 

 

 

 

 

 

A look at a scale from a different angle. You can also see white spots running along the stem. These are stomata.

 

 

 

 

 

 

 

 

 

 

 

Psilotum has the simplest arrangement of vascular tissue, a protostele.

 

 

 

 

 

Here is a picture of the stele. Locate the xylem, phloem, and endodermis. The metaxylem is in the centre with the protoxylem extending out as arms (exarch). It should look familiar since it is very similar to the root section you saw in Lab #3 and like primary plant roots is a protostele. The phloem would be between the arms of the protoxylem. You may see the endodermis just outside the primary phloem. Ther pericycle is between the endodermis and the conducting tissues (xylem and phloem).

 

 

 

 

 

 

 

 

 

A closer look at a portion of the stele. Can you identify the protoxylem and metaxylem?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Here is an unlabeled picture. You should be able to identify the different layers and cell types.

 

 

 

 

 

 

 

Older stems look a little different.

 

 

 

 

 

 

 

 

 

 

This is a picture of the outer portion of the stem.

 

 

 

 

 

 

 

 

This is a picture of the outer portion of an older stem.

 

 

 

 

 

 

 

 

 

STEM
SPORANGIUM
STELE TYPES

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