Underlay of a fern

Transcript

Frond dissection

Fronds can be simple and undivided like the leather leaf fern, or pinnate (once divided) like the thread fern. More commonly, fronds are bipinnate (silver fern) or tripinnate (hen and chickens fern).

Image acknowledgements: University of Waikato, Steve Attwood, Public domain and Museum of New Zealand Te Papa Tongarewa

Sori position

The sori may be located on the edge of the pinna or away from the pinna margin.

Image acknowledgement: Museum of New Zealand Te Papa Tongarewa

Sorus

Each sorus is a cluster of sporangia. The shape and position of the sori are important for identification of ferns. They provide the main features for identifying the different genera. Sori can be round, oval, oblong or considerably elongated. They may occur on the edge of the pinna or away from the edge. With a 10x hand lens, you’ll be able to see that the sori are composed of numerous, small, round bodies that are the sporangia.

Image acknowledgement: Museum of New Zealand Te Papa Tongarewa

Indusium

A flap of tissue that protects the sori in some ferns. This can take a variety of forms. When spores are mature and ready for release, the indusia usually shrivel or bend backwards to expose the sporangia. Occasionally, if the indusia completely cover the sporangia. they may tear irregularly.

Image acknowledgement: Museum of New Zealand Te Papa Tongarewa

Sporangium

The reproductive structures on the underside of the frond. Each sporangium is a capsule that contains spores. They are usually aggregated into clusters called sori. The position and arrangement of the sporangia are very important for the identification of ferns. Fronds that have sporangia on their underside are fertile, and those that don't are sterile.

Image acknowledgement: Museum of New Zealand Te Papa Tongarewa

Spore

A single cell. Spores are produced in capsules called sporangia. Most ferns produce 64 spores in each sporangium. Sporangia are aggregated into clusters called sori. When mature, the spores are released from the sporangia. Once released, the spores germinate readily on contact with damp soil.

Image acknowledgement: Australasian Pollen and Spore Atlas, Creative Commons