Members of this genus are extremely diverse, ranging in size from plants a fraction of an inch (a few mm) high to those that are bushlike and 39 in. (1 m) or more high. While most grow as upright plants, some grow along the ground like vines. Most Drosera species are perennials, but a few are annuals. They grow in all climates from tropical to arctic and from wet to dry. (Fig. 4-1)
The leaves of Drosera plants consist of a leaf blade and either a distinct petiole or one which is continuous with the shape of the blade. Leaf blade shape is extremely variable within the two major categories, broad and thread-like blades. Within the broad blade type, the overall shape varies from circular to spathulate to linear. The thread-like leaf blades are either simple or divided into segments which are long and thin. (Fig. 4-2) In both types the petiole is usually distinguishable from the blade by the absence of tentacles.
Tentacles or stalked glands exist on the adaxial surfaces and margins of the leaf blade and, in some cases, on the leaf petiole. The stalked glands lure, capture and digest prey. The stalkless, sessile glands are found on practically all exposed surfaces including the tentacle stalk and are the structures which absorb digested materials.
The leaves form a rosette in some species while in others they are borne along upright or creeping stems. Some species have both a basal rosette of leaves and leaves borne on an elongated stem.
Above-ground parts of the plants arise from rhizomes, roots or tubers.
The flowers are borne singly or in clusters. Petal color varies and includes shades of almost all colors. Petals and sepals usually number 5 per flower, each with 1 compound ovary and 5 stamens. Flowers usually open in bright light during the late morning to early afternoon, closing later in the day. The sequence of flower opening proceeds from the bottom of the scape upward, with the lowest flower on the scape opening first. Usually one or more flowers open each day.
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