parenchyma

noun3

1. •
   The functional tissue of an organ as distinguished from the connective and supporting tissue.
2. •
   The cellular tissue, typically soft and succulent, found chiefly in the softer parts of leaves, pulp of fruits, bark and pith of stems, etc.
3. •
   Cellular tissue lying between the body wall and the organs of invertebrate animals lacking a coelom, such as flatworms.

   • [I]n a Sponge, the Parenchyma, it seems, is but a kind of mucous gelly, which is very easily and cleerly wash'd away. — 1665