hormogonium
noun
hor·mo·go·ni·um ˌhȯr-mə-ˈgō-nē-əm 
plural hormogonia ˌhȯr-mə-ˈgō-nē-ə
: a portion of a filament in many cyanobacteria that becomes detached as a reproductive body
Word History
Etymology
New Latin, from Greek hormos chain, necklace + New Latin -gonium — more at series
First Known Use
1880, in the meaning defined above