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[4] [5] "Frond" is commonly used to identify a large, compound leaf, but if the term is used botanically to refer to the leaves of ferns and algae it may be applied to smaller and undivided leaves. Fronds have particular terms describing their components. Like all leaves, fronds usually have a stalk connecting them to the main stem.
In orchids, the stipe or caudicle is the stalk-like support of the pollinia. It is a non-viscid band or strap connecting the pollinia with the viscidium (the viscid part of the rostellum or beak). A stipe is also a structure found in organisms that are studied by botanists but that are no longer classified as plants.
Two specimens of Laminaria hyperborea, each showing the rootlike holdfast at lower left, a divided blade at upper right, and a stemlike stipe connecting the blade to the holdfast. Further information: Thallus , Holdfast (biology) , Stipe (botany) , Lamina (algae) , and Pneumatocyst
Each frond consists of a stipe (stalk) that is covered in light-brown scales towards the base and short glandular hairs further up. [5] [6] The stipes generally measure between 1/4 to 1/3 the length of the frond [6] and support a leaf blade that is lance-oblong [5] in shape.
The parts of a kelp thallus include the holdfast (anchor), stipe (supports the blades) and the blades (for photosynthesis). [2] The thallus of a fungus is usually called a mycelium. The term thallus is also commonly used to refer to the vegetative body of a lichen. In seaweed, thallus is sometimes also called 'frond'.
As many as 40,000 leaflets have been counted on a single frond. [5] The stipes are thick, black, very rough to the touch, and are similarly covered in black scales with marginal spines. S. medullaris can be readily distinguished from related species by the hexagonal stipe scars on the trunk, and by the scales with spines on their margins. [6] [7]
The fronds are of two types. Fertile (spore-bearing) fronds have stipes (stalks) that are usually much longer than those of sterile fronds. The blade (lamina) of the frond is usually 3–6 cm (1.2–2.4 in) long by about 2–4 cm (0.8–1.6 in) wide, with a heart-shaped base and a somewhat rounded apex. It is held at an angle to the stipe.
The broad, lance shaped, bipinnate-pinnatifid to tripinnate fronds can reach 5 metres (16 ft)) in length. Stipe is long and has a line of white, stitch like dashes along its length. Rachis and stipe are covered in white-brown and darker orange-brown scales. The trunk can become smooth with age and may display oval scars left from fallen fronds. [4]