When closely arranged on a tray, different pieces are often separated by green strips called "baran" or "kiri-zasa" (切り笹). These dividers prevent the flavors of neighboring pieces of sushi from mixing and help to achieve an attractive presentation. Originally, these were cut leaves from the "Aspidistra elatior" (葉蘭 "haran") and "Sasa veitchii" (熊笹 "kuma-zasa") plants, respectively. Using actual leaves had the added benefit of releasing antimicrobial phytoncides when cut thereby extending the limited shelf life of the sushi. Sushi bento boxes are a staple of Japanese supermarkets and convenience stores. As these stores began rising in prominence in the 1960s, the labor-intensive cut leaves were increasingly replaced with green plastic in order to lower costs. This coincided with the increased prevalence of refrigeration which acted to extend the shelf life of sushi without the need for the cut leaves. Today the plastic strips are commonly used in sushi bento boxes and to a lesser degree in sushi presentations found in sushi bars and restaurants. In store-sold or to-go packages of sushi, the plastic leaf strips are often used to prevent the rolls from coming into early or unwanted contact with the ginger and "wasabi" included with the dish.