Morphology
Below: Discoid holdfast (with epiphyte). Mouse over picture for back view.
Prionitis
lanceolata is usually dark red, and between 20-50 cm in height.
It has a discoid holdfast which usually has multiple stipes growing
from it. The thallus* is erect,
and there is no clear distinction between the stipes* and
the primary blades, which are both relatively flat. Branching is
roughly dichotomous, with many irregularities. Secondary blades
grow in a pinnate* fashion,
with parallel rows of pinnules (secondary blades) running down
the lateral margins of the primary blades.
While the above describes
a typical P. lanceolata, there are a wide variety of morphologies
expressed depending on the individual's habitat. In general, the higher an
individual lives, the smaller, more branched, and lighter in color it is, while
the lower individuals are larger, darker, and less frequently branched. For
more details on this, see Morphological Variation in
the Ecology section.
Internal Anatomy
The cortex is the outermost layer of cells and is made up of very small, round cells arranged in rows. These cells contain the photosynthetic pigments, including phycoerythrin, which accounts for their red color. The cortex is usually 5-12 cells thick. The transitional layer is more loosely arranged, with large, round cells arranged in a more scattered fashion. The medulla is the innermost layer and is composed of elongate filaments that run longitudinally through the thallus.
Created by Alice Chiu, 2003. Images may be used with permission.