Kingdom: Plantae or Protista
Classification controversy:Further proving that Prionitis lanceolata is a shifty fellow, in the past it has been classified under several other genera. Harvey, one of the first scientists who characterized it, originally thought it was Gelidium. It has also been mistaken for Sphaerococcus (all members in this genus have since been reassigned) and Grateloupia. In fact, a paper published in 2001 suggests that Prionitis species should be included in the genus Grateloupia, based on morphological and molecular similarities between the two genera. The authors especially make note of similarities between vegetative and reproductive structures as well as genetic similarities of a specific gene sequence (ribulose-1,5-bisphosphate carboxylase/oxygenase).
It has been a classical debate whether algae belong to the plants or the protists. Algae are not as complex as members of the plant kingdom, since they lack vascular tissue, true roots, and other such structures. However, most algae are considerably more complex than protists, which are almost wholly unicellular and are not photosynthetic. Despite this, Protista is currently the more acceptable kingdom designation for the algae.
Informally called "red algae," members of this division derive their color from phycoerythrin which is their dominant photosynthetic pigment. They store their food as floridean starch. Most are perennial* and dioecious*. Nonmotile spores and gametes are a unique characteristic of the reds.
The morphology of female reproductive structures and post-fertilization events are the distinguishing characteristics between families, even though vegetative structures are more practical for identification. However, general morphological characteristics include the thallus* being multiaxial*, erect, and mostly bladelike. Tetrasporangia* are cruciately* divided and are usually isolated just beneath the surface of the thallus or loosely aggregated in sori*. Spermatangia* are usually in superficial patches.
Created by Alice Chiu, 2003. Images may be used with permission.