The complex permanent tissues are made of more than
one type of cells.
They are of two types

(i) Xylem
(ii) Phloem

The characteristic features of collenchymatous tissues
are listed below
(a) It is present only in layer below the epidermis in
dicotyledonous plants.
(b) It is found either as a homogeneous layer or in
patches.
(c) Collenchyma consists of cells which are much
thickened at the corners due to a deposition of
cellulose, hemicellulose and pectin.
(d) The cells may be oval, spherical or polygonal and
often contain chloroplasts.
(e) These cells assimilate food, when they contain
chloroplasts.