1. Choose a type of habit (overall structure).
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Algae are colonial - cells united in packets, either joined side-to-side, loosely attached, united in common jelly, etc - but not solely joined end-to-end as in a filament.
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Algae are unicellular - not joined to neighbouring cells (even with colourless mucilage)
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Algae are filamentous (either cells joined end-to-end or comprised of long tubes without cell walls, may be branched or unbranched, or like a net)
