Arachnoid (botany)
Arachnoid as a descriptive term in botany, refers to organs such as leaves or stems that have an external appearance similar to cobwebs from being covered with fine white hairs, usually tangled. Such material is one common cause of plants having a grey or white appearance.Jackson, Benjamin, Daydon; A Glossary of Botanic Terms with their Derivation and Accent; Published by Gerald Duckworth & Co. London, 4th ed 1928 The usages of various authors in distinguishing between "arachnoid" and a few other terms referring to hairiness, such as floccose, pubescent, tomentum, cottony, or villous, tend to be arbitrary, but as a rule the term is best reserved for hairiness lighter than a felted layer, and inclined to rub off or to be easily damaged in other ways. The arachnoid appearance is common on the leaves and stems of various sclerophyllous members of the Asteraceae, such as some thistles. Nonetheless, "cobwebbiness" is a subjective impression, and in the likes of ''Hayworthia arachnoid ...
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Eriocephalus Africanus IMG 5720
''Eriocephalus'' is a genus of African flowering plants in the daisy family. General description The genus ''Eriocephalus'' appears in the ''Species Plantarum'' of Carl Linnaeus, item 926 (1753), and was dealt with by William Henry Harvey in Flora Capensis 3: 200 (1865) The plants are more or less sclerophyllous bushes or shrublets, some species tending to be thorny, leaves silky-greyish, most species are finely villous, but some are glabrous. They have a characteristic, rather spicy aroma, especially when bruised. This has been compared to the aroma of rosemary, though it is not convincingly so. However, the plants have been used similarly in cooking. The leaves are generally ericoid, alternate or sub opposite, often fascicled. The flowering heads are small, with short, racemose or subumbellate peduncles. In a few species the flowers are solitary. The flowers are heterogamous, a few female florets in each head occurring together with several bisexual, sterile disk-floret ...
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Arachnoid Leaves Of Unidentified Gazania 2012 07 05 7252s
Arachnoid may refer to: * Relating to arachnids * Arachnoid (astrogeology), a geological structure found only on the planet Venus * Arachnoid (botany), referring to organs with a cobwebby exterior appearance * Arachnoid granulation, small protrusions of the arachnoid mater * Arachnoid mater, a layer of the meninges, membranes that contain the central nervous system See also * ''Arkanoid is a 1986 block breaker arcade game developed and published by Taito. In North America, it was published by Romstar. Controlling a paddle-like craft known as the Vaus, the player is tasked with clearing a formation of colorful blocks by deflect ...

Haworthia Arachnoidea - Cobweb Aloe
''Haworthia'' is a large genus of small succulent plants endemic to Southern Africa (Mozambique, Namibia, Lesotho, Eswatini and South Africa). Like the aloes, they are members of the subfamily Asphodeloideae and they generally resemble miniature aloes, except in their flowers, which are distinctive in appearance. They are popular garden and container plants. Description and characteristics ''Haworthias'' are small succulent plants, forming rosettes of leaves from to exceptionally in diameter, depending on the species. These rosettes are usually stemless but in some species stems reach up to . The inflorescences of some species may exceed in height. The plants can grow solitary or can be clump-forming. Many species have firm, tough, fleshy leaves, usually dark green in colour, whereas others are softer and contain leaf windows with translucent panels through which sunlight can reach internal photosynthetic tissues. Their flowers are small, and generally white. Though they ...
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Cephalocereus Senilis
''Cephalocereus senilis'', the old man cactus, is a species of cactus native to Hidalgo and Veracruz in central Mexico. It is threatened in the wild, but widespread propagation and popularity in cultivation have reduced the demand on wild populations. Description ''Cephalocereus senilis'' is a tall, columnar species with clusters of stems that may grow to 5–15 m tall; the individual stems are usually unbranched, being unable to withstand the weight of side branches adequately. The most striking feature is the shaggy coat of long, white hairs suggestive of unkempt hair on an old man. The coat is a particularly striking silvery white on the young cactus; as the plant ages the stem begins to lose its covering. The flowers are red, yellow, or white, though the plant may not flower until 10–20 years old. Morphology and function of the coat The hairs are modified spines and they make many a plant appear almost snow-white; they serve to protect the plant from frost and sun. Howeve ...
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Cobweb
A spider web, spiderweb, spider's web, or cobweb (from the archaic word '' coppe'', meaning "spider") is a structure created by a spider out of proteinaceous spider silk extruded from its spinnerets, generally meant to catch its prey. Spider webs have existed for at least 100 million years, as witnessed in a rare find of Early Cretaceous amber from Sussex, in southern England. Many spiders build webs specifically to trap and catch insects to eat. However, not all spiders catch their prey in webs, and some do not build webs at all. "Spider web" is typically used to refer to a web that is apparently still in use (i.e. clean), whereas "cobweb" refers to abandoned (i.e. dusty) webs. However, the word "cobweb" is also used by biologists to describe the tangled three-dimensional web of some spiders of the family Theridiidae. While this large family is known as the cobweb spiders, they actually have a huge range of web architectures; other names for this spider family include tang ...
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Leaf
A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, flower, and fruit collectively form the shoot system. In most leaves, the primary photosynthetic tissue is the palisade mesophyll and is located on the upper side of the blade or lamina of the leaf but in some species, including the mature foliage of ''Eucalyptus'', palisade mesophyll is present on both sides and the leaves are said to be isobilateral. Most leaves are flattened and have distinct upper (adaxial) and lower ( abaxial) surfaces that differ in color, hairiness, the number of stomata (pores that intake and output gases), the amount and structure of epicuticular wax and other features. Leaves are mostly green in color due to the presence of a compound called chlorophyll that is essential for photosynthesis as it absorbs light ...
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Glossary Of Botanical Terms
This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary of leaf morphology. For other related terms, see Glossary of phytopathology, Glossary of lichen terms, and List of Latin and Greek words commonly used in systematic names. A B ...
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Felted
A felted material is a hairy or filamentous (hairy-like) fibre that is densely packed or tangled, forming felt or felt-like structures. Anatomy and zoology The dermis is described in Gray's Anatomy as "felted connective tissue, with a varying amount of elastic fibers and numerous blood vessels, lymphatics, and nerves." When describing the external coat of an artery (the ''tunica adventitia''), Gray said that it "...consists mainly of fine and closely felted bundles of white connective tissue..." In such classes of connective tissue the felted structure helps with resistance to tearing by distributing localised stresses, and it imparts shock absorption and elasticity in two or three dimensions at once regardless of the shape of the tissue. In other words, certain types of felting can yield controllable isotropy or anisotropy in the behaviour of a structure. Mammals Although truly felted hair on healthy mammals is unusual, many animals, especially in seasonally cold or wet ...
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Asteraceae
The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae were first described in the year 1740. The number of species in Asteraceae is rivaled only by the Orchidaceae, and which is the larger family is unclear as the quantity of extant species in each family is unknown. Most species of Asteraceae are annual, biennial, or perennial herbaceous plants, but there are also shrubs, vines, and trees. The family has a widespread distribution, from subpolar to tropical regions in a wide variety of habitats. Most occur in hot desert and cold or hot semi-desert climates, and they are found on every continent but Antarctica. The primary common characteristic is the existence of sometimes hundreds of tiny individual florets which are held together by protective involucres in flower heads, or more technicall ...
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Thistle
Thistle is the common name of a group of flowering plants characterised by leaves with sharp prickles on the margins, mostly in the family Asteraceae. Prickles can also occur all over the planton the stem and on the flat parts of the leaves. These prickles are an adaptation that protects the plant from being eaten by herbivores. Typically, an involucre with a clasping shape similar to a cup or urn subtends each of a thistle's flower heads. The comparative amount of spininess varies dramatically by species. For example, ''Cirsium heterophyllum'' has minimal spininess while ''Cirsium spinosissimum'' is the opposite. Typically, species adapted to dry environments have greater spininess. The term thistle is sometimes taken to mean precisely those plants in the tribe Cardueae (synonym: Cynareae), especially the genera '' Carduus'', ''Cirsium'', and ''Onopordum''. However, plants outside this tribe are sometimes called thistles. Biennial thistles are particularly noteworthy for ...
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Thorns, Spines, And Prickles
In plant morphology, thorns, spines, and prickles, and in general spinose structures (sometimes called ''spinose teeth'' or ''spinose apical processes''), are hard, rigid extensions or modifications of leaves, roots, stems or buds with sharp, stiff ends, and generally serve the same function: physically deterring animals from eating the plant material. Description In common language the terms are used more or less interchangeably, but in botanical terms, thorns are derived shoots (so that they may or may not be branched, they may or may not have leaves, and they may or may not arise from a bud),Simpson, M. G. 2010. "Plant Morphology". In: ''Plant Systematics, 2nd. edition''. Elsevier Academic Press. Chapter 9.Judd, Campbell, Kellogg, Stevens, Donoghue. 2007. "Structural and Biochemical Characters". In: ''Plant Systematics, a phylogenetic approach, third edition''. Chapter 4. spines are derived from leaves (either the entire leaf or some part of the leaf that has vascular bundles ...
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Arachnoid (other)
Arachnoid may refer to: * Relating to arachnids * Arachnoid (astrogeology), a geological structure found only on the planet Venus * Arachnoid (botany), referring to organs with a cobwebby exterior appearance * Arachnoid granulation, small protrusions of the arachnoid mater * Arachnoid mater, a layer of the meninges, membranes that contain the central nervous system See also * ''Arkanoid is a 1986 block breaker arcade game developed and published by Taito. In North America, it was published by Romstar. Controlling a paddle-like craft known as the Vaus, the player is tasked with clearing a formation of colorful blocks by deflect ...