The term 'WOOD COMB FORM' is composed of four crossword solutions: LIGNI (5 letters), XYL (3 letters), HYLO (4 letters), and LIGN (4 letters). LIGNI is a type of wood, also known as lignified tissue, which is composed of cells that have become hardened and impregnated with lignin. XYL is a type of wood, also known as xyloid tissue, which is composed of cells that are not hardened and impregnated with lignin. HYLO is a type of wood, also known as hyloid tissue, which is composed of cells that are hardened but not impregnated with lignin. Finally, LIGN is a type of wood, also known as lignified tissue, which is composed of cells that have become hardened and impregnated with lignin. All four of these types of wood are used to form various wooden objects, such as furniture, tools, and musical instruments.