Monterey Bay Aquarium Research Institute
Marine Botany

Egregia menziesii Morphology

Before you read all about the morphology of Egregia menziesii, look at this picture of a very rugose terminal lamina.  

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Egregia menziesii individuals consist of a holdfast, stipe, and  a varying number of fronds.  Fronds include the tough, flattened rachis, covered with laterally oriented blades and 
pneumatocysts.  At the end of the rachis, following a blade-less meristematic region, is the terminal lamina, which is also flattened, but wider and not as tough as the rachis (see figure).  
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Figure redrawn from Friedland and Denny, 1995 (see reference below (1)).  
 
  • The whole plant can usually grow to be up to 5 meters tall, although some have been found to grow up to 7.5 meters tall.  
  • The holdfast made up haptera can be up to 20 centimeters in diameter, and is usually not disc-shaped.  
  • The flattened stipe tends to be between 2.5 and 3.5 centimeters broad, with 6-25 branches.  The branches will be 3-6 cm in length before the frond begins.  The surface of the stipe as well as the rachis is densely covered with small, blunt tubercules.  
  • The blades of a single frond will all be about the same length, but the length and width of blades vary greatly from plant to plant (up to 6 cm. long).  Smaller blades containing sporangia in sori are found in amongst the other blades.  
  • The pneumatocysts are used as gas-filled bouyancy devices.  
  • They range from ellipsoid to subspherical, and are regularly tuberculated at their free end.   

Both the microscopic gametophyte and macroscopic sporophyte have a filamentous morphology, with the branches of the filaments free from one another.

As a young plant, the E.menziesii sporophyte is difficult to differentiate from other Laminariales, basically being made up of holdfast, small stipe and single to multiple terminal laminae.

As a member of the order Laminariales, Egregia menziesii, unlike many other algae, and more like angiosperms, contains several different tissue and cell types.  These include a photosynthetic epidermis, cortex, medulla, sieve tubes, and mucilage ducts (3) .

You can begin to see the differentiation in these microscope pictures of a young sporophyte cross-section (slide courtesy of Hopkins Marine Station).
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References for this page:
(1) Friedland, Michelle T., and Mark W. Denny.   "Surviving hydrodynamic forces in a wave-swept environment: Consequences of morphology in the feather boa kelp, Egregia menzeisii (Turner)."   Journal of Experimental Marine Biology and Ecology (1995) 190: 109-133.

(2) Abbott, Isabella A., and George J. Hollenberg. Marine Algae of California. Stanford University Press, CA. 1976.

(3) Lobban, Christopher S. and Paul J. Harrison.  Seaweed Ecology and Physiology. Cambridge
          University Press, New York.   1997.


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Last updated: Feb. 05, 2009