I'm confused over the two terms vascular cambium and intrafascicular cambium.
Is vascular cambium the same as intrafascicular cambium?
I know nothing about plant physiology but I googled your question and here is what I found
The vascular cambium (plural cambia) is a plant tissue located between the xylem and the phloem in the stem and root of a vascular plant, and is the source of both the secondary xylem growth (inwards, towards the pith material at the center of plant, often dead and/or deteriorated, that is composed of parenchyma tissue) and the secondary phloem growth (outwards [to the bark, rough or smooth, of the plant]). It is a cylinder of unspecialized meristem cells that divide to give new cells which then specialize to form secondary vascular tissues.
Intra fascicular cambium
The cambial strip which is present between the primary xylem and primary phloem is known as the intra fascicular cambium. The intra fascicular cambium is also known as the vascular cambium. During the secondary growth the cambial ring is formed by the inter connection of the intra fascicular and inter fascicular cambium. - See more at: http://www.biology.lifeeasy.org/5040/what-is-intrafascicular-cambium#sthash.aY3SPblI.dpuf
What is the difference between fascicular cambium and inter fascicular cambium?
The cambium present within the vascular bundle is called intra fascicular cambium or vascular cambium. It is present between the primary xylem and primary phloem. The intra fascicular cambium is primary in origin.
The new strip of cambium which is formed from the permanent cells of inter fascicular parenchyma is called the inter fascicular cambium. The inter fascicular cambium is secondary in origin since it is derived from the permanent cells of medullary rays.
If the above definitions don't help, you should include in your question why these definitions don't help and what is unclear.
The Vascular cambium is responsible for secondary growth, which is growth in thickness. Whereas, primary is growth in length. Once, the length-wise growth of the xylem and phloem are accomplished, growth in thickness or growth inwards through the vascular cambium occurs; it occurs in wood-based plants.
Vascular cambium is made of two parts. one is interfascicular vascular cambium and other is intra fascicular vascular cambium. The part between xylem and phloem is called intra fascicular vascular cambium.