Zool. Pl. -ia. [mod.L., f. Gr. σύν SYN- + δένδρον tree + -ium.] The thick fat quadrate disc suspended from the umbrella by the dendrostyles in rhizostomous hydrozoans.
1859. Huxley, Oceanic Hydrozoa, i. 18. In the Rhizostomidæ a complex tree-like mass … is suspended from the middle of the umbrella…. The main trunks of the dependent polypiferous tree … unite above into a thick flat quadrate disc, the syndendrium, which is suspended by … the dendrostyles.
