$\rightarrow$ In the spring season, cambium is very active and produces a large number of xylary elements having vessels with wider cavities.

$\rightarrow$ In spring season, the number of leaves increases. So for transport more number of vessels are needed.

$\rightarrow$ The wood formed during this season is called spring wood or early wood.

$\rightarrow$ The spring wood is lighter in colour and has a lower density.

$\rightarrow$ Autumn wood : In winter, the cambium is less active and forms xylary elements that have narrow vessels and this wood is called autumn wood or late wood.

$\rightarrow$ Autumn wood is darker and has a higher density.

$\rightarrow$ Annual Rings : Spring wood and autumn wood that appear as alternate concentric rings, constitute the annual ring. Annual rings seen in a cut stem give an estimate of the age of the tree.