The most primitive type of stele is

The most primitive type of mammalian placenta is

The most primitive type of mammalian placenta is

Simplest type of stele is

Simplest type of stele is

The most primitive mollusc is

The most primitive mollusc is

The most primitive mollusc is

[A]: Protostele is most simple primitive type of stele. [R]: According to Histogen theory there are three distinct apical layers which give rise to distinct tissue system of the body.