#cactus

• Aphylly — The biological state, trait, or evolutionary phenomenon consisting of the complete, congenital, or adaptive absence of leaves in a plant or vegetative organ; it represents a major xerophytic modification optimized to minimize water loss.
• Agave filifera — A small to medium-sized species of succulent plant within the genus Agave, native to the arid regions of central Mexico. It is easily recognized due to its unique morphological feature: its rigid, narrow, dark green leaves display thin, ornamental white threads along the margins, resembling elastic filaments (fibers) that naturally peel off as the leaf matures.
• Agave victoriaereginae — A small-sized, extremely rare, and protected species of succulent plant native to the Chihuahuan Desert in northern Mexico, classified in the Asparagaceae family. It is widely considered one of the most beautiful and geometric agave species in the world, characterized by a compact, rigid, and spherical rosette. Its short, thick, and triangular leaves are matte dark green, decorated with striking, angular white lines that look hand-painted. The margins are completely smooth and toothless, with the plant bearing only a single short, black terminal spine.
• Ancistrocactus — A genus of succulent plants in the family Cactaceae, native to the arid and semi-desert regions of the southern United States (Texas) and northern Mexico. It comprises relatively small, globular to cylindrical cacti with well-defined ribs and areoles bearing strong central spines, at least one of which is long and sharply hooked, a morphological feature that gives the genus its name.
• Ancistrocactus brevihamatus — A species of cactus endemic to the arid regions of Texas and northern Mexico, characterized by small globular or cylindrical stems, pronounced ribs, and strong central spines heavily hooked like a fishhook. The plant exhibits extreme adaptation to deep drought and develops bell-shaped flowers of greenish-yellow, pink, or reddish-brown color, highly valued in succulent collections for its spectacular defensive morphology.
• Ancistrocactus megarhizus — An exotic species of miniature cactus native to the arid regions of Tamaulipas, Mexico, remarkable for its huge, tuberous taproot that often exceeds the volume of its aerial stem. The plant uses this massive underground structure as a strategic reservoir for water and nutrients, allowing it to survive in hyper-arid environments, while its outer globular body bears harsh yellow or grayish spines and produces spectacular greenish-yellow flowers.
• Ancistrocactus scheerii — A species of cactus native to the border regions of Texas and northern Mexican states, recognized by its oval or cylindrical deep green stem covered in spirals of prominent tubercles and rigid spines, with the central one ending in a well-defined hook. This rare plant develops elongated, bell-shaped flowers of greenish-yellow or purplish hue, being perfectly adapted to survival in extremely dry limestone soils and valued for its ecological resilience.
• Ancistrochilus — A small genus of epiphytic and sympodial orchids, native to the tropical rainforests of West and Central Africa, characterized by unusual onion-shaped or flask-like pseudobulbs and deciduous leaves. The name refers to the flower's lip which is sharply recurved like a hook, a specific morphological adaptation for guiding insect pollinators within dense forest habitats.
• Aporocactus — A genus of epiphytic or lithophytic plants in the family Cactaceae, native to the mountainous regions and forests of Mexico, characterized by long, slender, cylindrical, and creeping or pendulous stems covered with fine spines and large, tubular, brightly colored pink, red, or crimson flowers. In modern horticulture, the most famous species is Aporocactus flagelliformis (rat-tail cactus), widely cultivated in hanging baskets.
• Aporocactus flagelliformis — A species of epiphytic cactus native to Mexico, belonging to the genus Aporocactus (recently also classified as Disocactus flagelliformis), commonly known as the rat-tail cactus. It is characterized by long, cylindrical, pendulous, and flexible stems that can reach up to one meter in length, covered with fine bristles and large tubular, bright pink or magenta flowers, making it one of the most widely cultivated hanging basket plants.
• Aporocactus martianus — A rare species of epiphytic or lithophytic cactus native to Mexico (endemic to Oaxaca state), belonging to the genus Aporocactus (classified by some taxonomists as Disocactus martianus). It is distinguished by thick, deeply ribbed green trailing or pendulous stems (bearing 8-10 pronounced ribs), reddish-brown acicular spines, and large, tubular, bright scarlet-red flowers that remain open both day and night.
• Areola — A small circular area, pigmented or structurally differentiated, surrounding a central point, such as the darker ring of skin around the nipple or the space bounded by the secondary vein ramifications of a leaf. In botany, the term also denotes the microscopic structure or cushion of hairs or spines specific to cacti (Cactaceae family), from which flowers, new branches, or defensive needles develop.
• Ariocarpus — A genus of cacti endemic to the semi-desert zones of Mexico and southern Texas, characterized by extremely slow growth, flattened globular stems, and unique, triangular or rocky tubercles lacking classic spines at maturity; these succulent plants have a massive taproot used as a water reservoir and are highly prized by collectors for their large flowers and mimetic appearance mimicking surrounding limestones.
• Ariocarpus retusus — A cactus species endemic to the arid and semi-desert regions of Mexico (genus Ariocarpus), characterized by the absence of spines in adult specimens and the presence of robust, triangular, grayish-green tubercles, often retuse or rounded at the apex. Commonly known as 'living rock', this globose cactus is extremely slow-growing and features a massive taproot, being bio-structurally adapted to survive within the cracks of limestone rocks.
• Ariocarpus trigonus — A cactus species endemic to northeastern Mexico, often classified as a subspecies or closely related variety of Ariocarpus retusus; it is structurally distinguished by its long, upward-curved, and sharply pointed tubercles, featuring a perfectly triangular (trigonous) cross-section. The plant resembles a rigid rosette, lacks spines, and produces spectacular yellow or cream-colored flowers during its blooming period.
• Arrojadoa — A genus of xerophytic plants within the Cactaceae family, endemic to the semi-arid regions of eastern Brazil, particularly inside the caatinga vegetation. It is characterized by slender, cylindrical, erect or decumbent, jointed stems that develop a woolly and bristly apical cephalium from which bright, tubular flowers emerge, adapted for hummingbird pollination.
• Arrojadoa penicillata — A particular cactus species within the Arrojadoa genus, endemic to the state of Bahia in Brazil. It is distinguished by slender, highly branched, and often shrubby stems whose segmented tips form a dense apical cephalium covered with fine, long hairs resembling a small brush (penicillate), from which vivid pink or purplish-red tubular flowers erupt.
• Arrojadoa rhodantha — A xerophytic species of cactus within the Arrojadoa genus, endemic to eastern Brazil (particularly in the states of Piauí, Ceará, Pernambuco, and Bahia), characterized by cylindrical, semi-erect or scrambling stems that develop a ringed apical cephalium covered with brownish or white wool and stiff reddish bristles. Its flowers are tubular, intense pink-magenta or bright red, adapted for hummingbird pollination within rocky caatinga habitats.
• Arthrocereus — A genus of succulent plants in the Cactaceae family, endemic to the mountainous and arid regions of Brazil, particularly in the state of Minas Gerais. These species are structurally characterized by thin, cylindrical, poorly branched or decumbent stems, covered with dense and fine spines, producing large, nocturnal, white or pale-pink flowers adapted for pollination by moths.
• Astrophytum — A genus of succulent plants within the Cactaceae family, native to the arid and semi-desert regions of Mexico and the southern United States (Texas). These cacti are characterized by globose or cylindrical stems, often lacking spines in adult state, decorated with prominent ribs and microscopic white dots formed by coarse hairs (trichomes), possessing a general star-like appearance reminiscent of a star or marine astroid.