Based on the number of xylem arch, the roots are known as the monarch, diarch, triarch, tetrarch and so on. The root of the gram plant (Cicer arietinum) possesses a tetrach condition, While that in the pea plant is triarch, In the dicotyledonous plants, the xylem plates usually extend into the centre to form a solid centre core without anypith and phloem patches a.re rather small.