Page 103 - Pharmacognosy 2 PG303

Pharmacognosy-2 (PG303) Level 2 Clinical Pharmacy-Pharm D

3- Stele: all tissues enclosed within the endodermis constitute the stele. The vascular tissues
i.e. phloem and xylem from he important part of the stele. The stele may be one of the
following types:

1- Protostele (Monostele): it is the primitive and simplest type, composed of a solid column
of xylem, surrounded by a band of phloem followed by the pericycle and surrounded by a
layer of endodermis. It has no pith.

2- Siphonostele (Medullated protostele): it is protostele, having central pith. Phloem is
present either outside of xylem (ectophloeic) or on both sides of xylem (amphiphloeic).

3- Solenostele: it is amphiphloeic siphonostele but with an additional endodermis bordering
the pith.

4- Dictyostele: it is solenostele, dissected to form a ring of separate small protosteles termed
meristeles e.g. Male fern.

5- Dissected siphonostele: it is siphonostele, dissected to form a ring of separate vascular
bundles with outer phloem and inner xylem, as in Angiosperms.

66