as axillary, subterranean branches that do not bear green leaves but only membranaceous, scale-like ones. A stolon of grasses is defined as a horizontal stem above or on the soil surface that often roots at the internodes. Plants with stolons In some Cyperus species the stolons end with the growth of tubers; the tubers are swollen stolons that form new plants. Some species of crawling plants can also sprout adventitious roots, but are not considered stoloniferous: a stolon is sprouted from an existing stem and can produce a full individual. Examples of plants that extend through stolons include some species from the genera Riccia, Argentina (silverweed), Cynodon, Fragaria, and Pilosella (Hawkweeds), Zoysia japonica, Ranunculus repens. Plants with long, slender stolons are referred to as sarmentose plants. Other plants with stolons below the soil surface include many grasses, Ajuga, Mentha, and Stachys. Several species of Irises have stolons attached to their rhizomes, including Iris stolonifera. Lily-of-the-valley (Convallaria majalis) has rhizomes that grow stolon-like stems called stoloniferous rhizomes or leptomorph rhizomes. A number of plants have stoloniferous rhizomes including Asters. These stolon-like rhizomes are long and thin, with long internodes and indeterminate growth with lateral buds at the node, which mostly remain dormant. In potatoes, the stolons start to grow within 10 days of plants emerging above ground, with tubers usually beginning to form on the end of the stolons. The tubers are modified stolons that hold food reserves, with a few buds that grow into stems. Since it is not a rhizome it does not generate roots, but the new stem growth that grows to the surface produces roots. See also BBCH-scale (potato). Hydrilla use stolons that produce tubers to spread themselves and to survive dry periods in aquatic habitats. Erythronium, commonly called Trout Lily, have white stolons growing from the bulb. Most run horizontally, either underground or along the surface of the ground under leaf litter. A number of bulbous species produce stolons, such as Erythronium propullans. Flowering plants often produce no stolons. Convolvulus arvensis is a weed species in agriculture that spreads by under ground stolons that produce rhizomes. In studies on grass species, with plants that produce stolons or rhizomes and plants that produce both stolons and rhizomes, morphological and physiological differences were noticed. Stolons have longer internodes and function as means of seeking out light and are used for propagation of the plant, while rhizomes are used