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Phycokey Morphology

Organization within Phycokey is based on separation of morphological features easily recognizable in a student-grade microscope.  The first level of separation is generally the most apparent:  unicells (single cells), colonies, and filaments.

Second, where useful, unicells are separated on the basis of flagellated and non-flagellated.  In other cases the presence or absence of an extracellular gelatinous sheath is useful.

Filamentous forms are separated into branched and unbranched, tapered or untapered, cell differentiation or not, sheath present (‘filaments’) or no sheath (‘trichomes’), and other attributes where applicable.

Additional characteristics useful in various groups include chloroplast characteristics (shape and number per cell), spores, cell connections in colonies and filaments.

Diatoms are further separated based on raphes (biraphes and monoraphes) or lack thereof (araphes), symmetry and pores (punctae).

Cyanobacteria are separated further on the basis of presence or absence of nitrogen-fixing heterocysts.

Conjugate greens (desmids and non-desmids) are separated from non-conjugate greens even though this is not directly and explicitly through their morphology.

In summary the navigation via morphology in Phycokey is similar to that used in standard dichotomous (bifurcate) keys, but with the added advantage, usually, of comparing more than two images at any level of decision that leads to a genus.  The cover page, for example, includes a representative image of 18 different classes.