To solve this problem, we need to identify which of the given plant tissues is composed of dead cells. Let's analyze each option:$\newline \bullet$Collenchyma:$\newline$ - Collenchyma is a type of plant tissue that provides support to growing parts of plants.$\newline$ - It is composed of living cells with thickened cell walls.$\newline$ - Therefore, collenchyma is not made up of dead cells.$\newline \bullet$Phellem:$\newline$ - Phellem, also known as cork, is a protective tissue in plants.$\newline$ - It is composed of dead cells with suberized cell walls, which makes it impermeable to water and gases.$\newline$ - Therefore, phellem is made up of dead cells.$\newline \bullet$Phloem:$\newline$ - Phloem is a complex tissue responsible for the transport of nutrients, particularly sugars, in plants.$\newline$ - It consists of both living (e.g., sieve tube elements, companion cells) and dead cells (e.g., phloem fibers).$\newline$ - However, the primary functional cells in phloem are living.$\newline \bullet$Xylem parenchyma:$\newline$ - Xylem parenchyma is a type of living cell found in xylem tissue.$\newline$ - It is involved in the storage and lateral transport of water and nutrients.$\newline$ - Therefore, xylem parenchyma is not made up of dead cells.$\newline$Based on the analysis, the correct answer is Option 2: Phellem, as it is composed of dead cells.