President Barack Obama (D-IL) won the popular vote in 26 states and the District of Columbia (denoted in blue) to capture 332 electoral votes. Former Governor Mitt Romney (R-MA) won the popular vote in 24 states (denoted in red) to capture 206 electoral votes.
Xylem consists of three different types of cells: Xylem parenchyma cells and xylem fiber cells, which simply provide structural support for the most important xylem cells, the tracheary elements (TE). The TE are completely dead at maturity, and act like pipes to allow water and dissolved minterals to flow through them. There are two types of tracheary elements: vessel elements and tracheids. Though they have some structural differences, these two types function in the same manner.
There are four types of xylem cells: 1  Xylem vessels: Consist of dead hollow cells because the walls are lignified and the cell contents disintegrate. 2  The lignin makes the cell wall impermeable so they are in effect waterproof. 3  It also makes the vessels extremely strong and prevents them from collapsing.