CELL TYPE CYTOPLASMIC FEATURES CELL WALL FEATURES 3-D GEOMETRY
Transfer Cell 

Subcategories based on location of wall ingrowths and tissue association in minor veins
  
Type Associated with
A Phloem (Specialized companion cell)
B Phloem (Specialized Phloem parenchyma)
C Xylem
(Non Bundle Sheath)
D Xylem (Bundle sheath)
 

 Large lobed Nucleus 

Little vacuolated 

Numerous Mitochondia 

Abundant Endoplasmic Reticulum

Microbodies with crystalline core 

 Labyrinth of unlignified secondary cell wall ingrowths that can be long filiform, y-shaped, or short papillate.  Note that these ingrowths are difficult to resolve with the compound light microscope. 
  
Type Cell ingrowths located
A All facets
B Only facets next to sieve tube elements
C Only facets next to tracheary elements
D Only facets next to tracheary elements
 
Transverse Isodiametric
Longitudinal  Isodiametric
 

Transfer Cell Consortium to improve endosperm filling