Pediocactus simpsonii

Last updated

Pediocactus simpsonii
Pediocactus simpsonii - Abby Benson 01.jpg
Pediocactus simpsonii blooming Mount Falcon Park, Jefferson County, Colorado
Status TNC G5.svg
Secure  (NatureServe) [1]
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Order: Caryophyllales
Family: Cactaceae
Subfamily: Cactoideae
Genus: Pediocactus
Species:
P. simpsonii
Binomial name
Pediocactus simpsonii
Synonyms [2]
List
    • Echinocactus simpsonii Engelm. (1863)
    • Echinocactus simpsonii f. minor (Engelm.) Schelle (1907)
    • Echinocactus simpsonii var. minor Engelm. (1863)
    • Echinocactus simpsonii var. robustior J.M.Coult. (1896)
    • Mammillaria purpusii K.Schum. (1894)
    • Mammillaria simpsonii (Engelm.) M.E.Jones (1893)
    • Mammillaria spaethiana Späth (1895)
    • Pediocactus hermannii W.T.Marshall (1954)
    • Pediocactus nigrispinus subsp. indranus (Hochstätter) Hochstätter (2003)
    • Pediocactus robustior (J.M.Coult.) Arp (1972)
    • Pediocactus simpsonii f. acklinii Hochstätter (1997)
    • Pediocactus simpsonii subsp. bensonii Hochstätter (1995)
    • Pediocactus simpsonii var. caespiticus Backeb. (1961)
    • Pediocactus simpsonii f. campestris Hochstätter (1997)
    • Pediocactus simpsonii f. dinosauriensis Hochstätter (1997)
    • Pediocactus simpsonii f. flaminggorgensis Hochstätter (1997)
    • Pediocactus simpsonii f. flinspachii Hochstätter (1997)
    • Pediocactus simpsonii var. hermannii (W.T.Marshall) W.T.Marshall (1957)
    • Pediocactus simpsonii subsp. idahoensis Hochstätter (1997)
    • Pediocactus simpsonii subsp. indranus (Hochstätter) Hochstätter (1995)
    • Pediocactus simpsonii var. indranus Hochstätter (1990)
    • Pediocactus simpsonii f. kuenzleri Hochstätter (1997)
    • Pediocactus simpsonii var. minor (Engelm.) Cockerell (1918)
    • Pediocactus simpsonii f. montanensis Hochstätter (1997)
    • Pediocactus simpsonii f. muehlii Hochstätter (1997)
    • Pediocactus simpsonii f. prairie Hochstätter (1995)
    • Pediocactus simpsonii subsp. robustior (J.M.Coult.) Hochstätter (1995)
    • Pediocactus simpsonii f. sandiamontanus Hochstätter (1997)

Pediocactus simpsonii, known by the common names mountain cactus, snowball cactus, and mountain ball cactus, is a relatively common cactus that has adapted to survive in cold and dry environments in high elevation areas of the western United States. It can be found at higher elevations than any other cactus in North America. While not a landscape dominating plant, it is a relatively common species and the most common member of the genus Pediocactus . Because of its beauty and adaptation to cold environments it is sometimes grown by gardeners in areas that have few other choices due to the limited number of cactuses with cold adaptations. Like many cactuses its populations are sometimes threatened by this desirability due to the theft or removal of plants from the wild by collectors.

Contents

Description

The body of this succulent plant is one or more enlarged rounded stems, 2.5–15 centimeters wide and 2.5–25 centimeters tall, though it usually is less than 15 centimeters in height. The shape of this stem is like an egg with the wider part towards the soil (ovoid) or like a ball shape (globose), but can be flattened out or sunken into the ground in appearance (depressed), particularly in winter. [3] [4] The surface of the plant is covered in pyramid shaped projections or branch-lets called tubercles. [5] [6] At the tip of each tubercle a round to oval structure 3 millimeters across called an areole. [3] [6] It is covered in fine hairs (villous) and is where the cluster of spines grow. The spines are quite hard and smooth and vary in color and size by position. [3] The spines at the center of the cluster number 4 to 11, are 5–21 millimeters long, and are a dark color such as reddish-brown or even black at the ends with a cream to yellow colored base. [3] The spines arrayed around the center (radial) number 12 to 35 per cluster, are 3–13 millimeters long, and are white in color. [3] [6]

Flowering and fruit

Pediocactus simpsonii pale yellow flower form near Unaweep Canyon, Mesa County, Colorado Pediocactus simpsonii - Flickr - aspidoscelis (1).jpg
Pediocactus simpsonii pale yellow flower form near Unaweep Canyon, Mesa County, Colorado

Pediocactus simpsonii has its flowers are grouped at the center-top of the stem and are surrounded by brown or white woolly hairs. The flower buds are blunt shaped. [5] The flowers are fragrant highly variable in color, the colored inner tepals (casually called petals) coming in white, pink, magenta, yellow, or yellow-green. [7] [3] The size of the flowers of Pediocactus simpsonii ranges from 1.2–3 centimeters across and 1–2.5 centimeters in depth. [3] On cloudy days and at night the flowers will usually remain partially closed. [8] [5] The inner tepals are 12–25 millimeters long and 4.5–9 millimeters wide. [3]

The scales and outer tepals of the flowers and buds have toothed edges, and may either have no deeper divisions (entire margin) or have a deep lobes like a pitchfork (laciniate), and generally have a wavy edge (undulate). The outer tepals have a greenish brown stripe down the middle and have a shape like rounded rectangle but with a tapered base (oblong-cuneate). They are 9–20 millimeters long and 3–6 millimeters wide. [3]

The center of the flower is filled with numerous pollen bearing filaments (stamens) that are golden yellow and 6–9 millimeters long. [5] [6] The style and stigma-lobes are yellowish. [5] The stamens are sensitive to touch and will move inward to clasp the style if stroked. [9] Flowering is from spring through early summer, May to June in Colorado. [7] [3]

Pediocactus simpsonii with fruits and withered flowers Pediocactus simpsonii - Simpson's hedgehog cactus - 53012656336.jpg
Pediocactus simpsonii with fruits and withered flowers

The fruit of Pediocactus simpsonii is a small rounded cylinder 6–11 millimeters long and 4.5–10 millimeters in diameter. The fruits are smooth, green tinged with red and filled with gray or black seeds. [6] [3] Its seeds are 2–3 millimeters by 1.5–2 millimeters. [3] When ripe the fruit dries out and splits open to release the seeds. [4]

When not in flower this species is very difficult to distinguish from other species of cactus, such as Pelecyphora vivipara (beehive cactus) another high elevation cactus. Pelecyphora vivipara has narrower tepals on its flowers and they have a fringed edge in contrast to the smooth edges of Pediocactus simpsonii's tepals. Additionally the flowers of P. simpsonii grow from near the tip of the tubricals instead of near the base, and lack the groove on one side of the tubrical. The hinged top of the ripe fruit of P. simpsonii is quite distinguishing, when present. [10] Young plants are also easily confused with Pediocactus knowltonii , but older plants with the dark central spines are quite distinct. [11]

Taxonomy

Pediocactus simpsonii illustrated Pediocactus simpsonii illustration 01.png
Pediocactus simpsonii illustrated

Pediocactus simpsonii was scientifically described by George Engelmann and originally given the name Echinocactus simpsonii in 1863. [2] The species was described from specimens collected in Utah's Butte Valley and the Kobe Valley to the west. [5] [12] In 1893 the botanist Marcus E. Jones published a paper moving the species to genus Mammillaria , though this did not become a standard name. The name that it is most commonly classified under as of 2023, Pediocactus simpsonii, was published by American botanists Nathaniel Lord Britton and Joseph Nelson Rose in 1913. [2] [13] [14] Though this name has been well accepted since that time, 21 species or subspecies have been published that are now regarded as taxonomic synonyms of P. simpsonii, including 16 described by Fritz Hochstätter in the 1990s and 2000s. [2]

The genus Pediocactus is small, consisting of just seven to nine species. [15] [16] Of these, only Pediocactus simpsonii is widespread or common. It is also quite variable in form and bloom leading some botanists to recognize many subspecies or to confuse it with other cactuses. [17]

Names

The species was named by Engelmann in honor of James H. Simpson, who was a surveyor and commander of the expedition to Utah in 1858–1859 where the first specimens were collected. [18] The genus name, Pediocactus, comes from Greek "pedion" for "a plain", which was thought to be the habitat of the genus. [19] [10] Common names for Pediocactus simpsonii related to its habitat include "mountain cactus", [3] "snowball cactus", [8] and "mountain ball cactus". [14] Because its range extends onto the plains it is also occasionally as the "plains cactus". [20] Based on its scientific name it is also called "Simpson's hedgehog cactus", [8] "Simpson's footcactus", [3] and "Simpson's ball cactus". [21] More generically it is called "pincushion cactus" [22] and "hedgehog cactus", as are a number of other species. [23]

Distribution and conservation

Very short, nearly flat Pediocactus simpsonii blooming in Teller County, Colorado Pediocactus simpsonii - Craig Martin 01.jpg
Very short, nearly flat Pediocactus simpsonii blooming in Teller County, Colorado

Pediocactus simpsonii is found throughout the interior western United States from Arizona and New Mexico in the south to Idaho and Montana in the north. It can also be found in Nevada, Utah, Wyoming, Colorado, and South Dakota. [14] [2] In Montana it is only found in the mountains in the southwest of the state near to the border with Idaho. [8] It if found throughout much of the southern, non-panhandle, portions of Idaho, excluding only the western edge. In Wyoming it grows in the southern and the western sides of the state. In Nevada it is found in the mountain ranges of the Great Basin in the eastern side of the state. Utah's populations can be found through much of the state where suitable habitat is found. In Colorado it grows in the foothills, mountains, and west slope of the state. It is found only in a few isolated populations in northern Arizona and is likewise found only in the mountains of northern New Mexico. [14] [8]

In 2013 NatureServe evaluated the species and found it to be globally secure, G5. At the state level they evaluated it as apparently secure (S4) in three states, Montana, Nevada, and Utah. In three other states, Idaho, New Mexico, and Wyoming it was evaluated as vulnerable (S3). They found it to be critically imperiled (S1) in Arizona and have not evaluated its status in Colorado or South Dakota. [1] The largest threat to the species is collection of plants by gardeners and for the plant trade. In some places it is as threaten by mining or development. [1]

Habitat

As many of its common names suggest, Pediocactus simpsonii mainly grows in mountains and other uplands. [24] Within these areas it grows on dry ground and on slopes. [7] It is found in association with ponderosa pine forests, pinyon-juniper woodlands, cool sagebrush steppes, growing under scrub oaks, and parts of the shortgrass prairie. [3] [9] It will also grow on bare rock outcrops, such as granite in Wyoming and sandstone outcrops in Colorado. It is very hardy for a cactus, one mountain valley where it grows successfully has recorded a low temperature of -47 °C. [24] The elevation range for the species is from 1400 to 3500 meters. [3] In New Mexico it is very rarely found below 1800 meters. [4] It grows at higher elevations than any other cactus in North America. [10] Average precipitation in its habitat is 25–30 centimeters a year, but may be as much as 50 centimeters. [25]

It is unclear if the species is extirpated by wildfires, though it has been observed colonizing a very small number of plots after low or medium intensity wildfires and being absent from another after a medium intensity fire. [26] The seeds of P. simpsonii on the plains of Colorado have an elaisome and are thought to be dispersed by ants. [27]

Cultivation

Pediocactus simpsonii illustrated by Mary Emily Eaton in 1922 Pediocactus simpsonii illustration 02.png
Pediocactus simpsonii illustrated by Mary Emily Eaton in 1922

The attractiveness of the "beautiful flowers" is noted even botanical texts [5] and so mountain cactus is a plant desired by gardeners for use in rock gardens in cold climates. [28] When grown in a garden setting the mountain cactus requires a loose soil that will not set too hard when it dries. Plants survive well with a growing medium that is two-thirds sand and one-third rotted leaves, with a layer of pure sand around the base of the plant. Rotting may occur if water remains around the plant. Flowering is reduced if mountain cactuses are not kept dry and cool during the winter season. [29] Though very hardy in cold climates, these cactuses will die if transplanted to a hot desert climate. [30]

Germination studies on mountain cactus seeds indicate some need of cold-moist stratification. Only 10% of seeds germinated at 21 °C after eight weeks where on the other hand 67% germinated at 4.5 °C in 17 days. Further tests found that the growth hormone gibberellic acid (GA3) would stimulate 70% germination of seeds that had been stored for several months when planted at 21 °C and even a sample that had been stored for around two years would sprout at 33% when treated with GA3. In contrast seeds stored for several months and planted at 4.5 °C and then raised to 21 °C only showed an 18% germination rate in 2–10 weeks. [31]

Related Research Articles

<i>Schlumbergera</i> Genus of plants (cacti)

Schlumbergera is a small genus of cacti with six to nine species found in the coastal mountains of south-eastern Brazil. These plants grow on trees or rocks in habitats that are generally shady with high humidity, and can be quite different in appearance from their desert-dwelling cousins. Most species of Schlumbergera have stems which resemble leaf-like pads joined one to the other and flowers which appear from areoles at the joints and tips of the stems. Two species have cylindrical stems more similar to other cacti.

<i>Toxicoscordion venenosum</i> Western North American flowering plant

Toxicoscordion venenosum, with the common names death camas and meadow death camas, is a species of flowering plant in the family Melanthiaceae. It is named for its well known toxic qualities, with both its common names and its scientific name referencing this. Because its nectar is also poisonous, it is mainly pollinated by the death camas miner bee, which specializes in collecting the toxic pollen for its young. It is native to western North America from New Mexico to Saskatchewan and west to the Pacific Ocean.

<i>Pediocactus</i> Genus of cacti

Pediocactus is a genus of cacti native to the Western United States. The genus comprises between 6 and 11 species, depending upon the authority. Species of this genus are referred to as hedgehog cacti, though that name is also applied to plants from the genera Echinocereus and Echinopsis. Species may also be referred to as pincushion cacti, a common name which is also applied to other genera.

<i>Sclerocactus</i> Genus of cacti

Sclerocactus is a genus of cacti. It comprises about 15 species, the exact number depending on the authority. These species are xerophytic. They are sometimes called 'fishhook cactus' or 'little barrels.'

<i>Pelecyphora missouriensis</i> Species of cactus

Pelecyphora missouriensis, the Missouri foxtail cactus and formerly Coryphantha missouriensis, is a species of low-growing North American cacti.

<i>Pediocactus bradyi <span style="font-style:normal;">subsp.</span> winkleri</i> Species of cactus

Pediocactus bradyi subsp. winkleri, commonly known as Winkler's cactus or Winkler's pincushion cactus, is a small cactus endemic to the state of Utah in the United States. It is known only from Emery and Wayne Counties.

<i>Frasera speciosa</i> Species of flowering plant in the gentian family

Frasera speciosa is a species of flowering plant in the gentian family (Gentianaceae) known by the common names elkweed, monument plant, and green gentian. When blooming it grows a tall stalk with numerous flowers that have purple dotted green petals. Each plant can flower just once before it dies.

<i>Pelecyphora sneedii</i> Species of cactus

Pelecyphora sneedii is a rare species of cactus known by the common names Sneed's pincushion cactus and carpet foxtail cactus. It is endemic to the Chihuahuan Desert of the southwestern United States and northwestern Mexico. It is a small, variable cactus with a lengthy taxonomic history, and is often subdivided into a number of subspecies or varieties. It is usually found on steep, rocky habitats, primarily of limestone geology, in desert scrub or coniferous forest. A species of conservation concern, P. sneedii faces threats from poaching, urban encroachment, and wildfires.

<i>Pediocactus sileri</i> Species of cactus

Pediocactus sileri is a rare species of cactus known by the common names Siler's pincushion cactus and gypsum cactus. It is native to southwestern Utah and northwestern Arizona in the United States. It is limited to a specific type of soil, individuals are often spaced far apart, and the species is threatened by a number of human activities such as off-road vehicle use, poaching, and uranium mining. This is a federally listed threatened species of the United States.

<i>Pediocactus bradyi</i> Endangered species of cactus

Pediocactus bradyi is a very rare species of cactus known by the common names Brady's pincushion cactus, Brady's hedgehog cactus, and Marble Canyon cactus. It is endemic to Arizona in the US, where it is restricted to Marble Canyon in Coconino County, though its exact distribution is not generally advertised due to poaching concerns. It is limited to a specific type of soil, it has a small distribution, and the species is threatened by a number of human activities. This has been a federally listed endangered species of the United States since 1979.

<i>Pediocactus knowltonii</i> Species of cactus

Pediocactus knowltonii is a rare species of cactus known by the common names Knowlton's miniature cactus, Knowlton's pincushion cactus, and Knowlton's minute cactus.

<i>Sclerocactus glaucus</i> Species of cactus

Sclerocactus glaucus is a rare species of cactus known by the common name Colorado hookless cactus. It is endemic to Colorado in the United States, where it is known only from the area between Grand Junction and Montrose. It is a federally listed threatened species.

<i>Sclerocactus sileri</i> Species of cactus

Sclerocactus sileri, the Siler fishhook cactus, is a rare and very small cactus found mostly in mineral-rich desert areas of intermediate elevations, notably in the American states of Utah, Nevada, and northern Arizona.

<i>Cochemiea conoidea</i> Species of cactus

Cochemiea conoidea, common name Texas cone cactus or Chihuahuan beehive, is a species of cactus native to southern United States to central Mexico.

Peniocereus striatus is a species of cactus known by several common names, including gearstem cactus, cardoncillo, jacamatraca, sacamatraca, and dahlia-rooted cactus. It is endemic to the Sonoran Desert, where it occurs in Baja California, Sinaloa, and Sonora in Mexico and Arizona in the United States.

<i>Penstemon caespitosus</i> Species of flowering plant

Penstemon caespitosus, commonly known as mat penstemon, is a summer blooming perennial flower in the large Penstemon genus. It is a widespread plant from near timberline to the foothills in the Southern Rocky Mountains and Colorado Plateau in North America. It is noted for its ground hugging growth habit and as a plant used in xeriscape and rock gardening.

<i>Castilleja rhexiifolia</i> Species of flowering plant

Castilleja rhexiifolia, commonly called rosy paintbrush, subalpine paintbrush, or rhexia-leaved paintbrush, is a species of plant in Orobanchaceae, commonly known as the broomrape family. They are a common flower found in moist habitats near or above timberline in the Rocky Mountains and the Pacific Northwest. Like most members of the Castilleja genus, they are partially parasitic plants.

<i>Pelecyphora robbinsiorum</i> Species of cactus

Pelecyphora robbinsiorum known by the common names Cochise pincushion cactus and Cochise foxtail cactus is a species of flowering plant in the family Cactaceae.

<i>Sisyrinchium demissum</i> Species of flowering plant in the blue-eyed grass genus

Sisyrinchium demissum, commonly called stiff blue-eyed grass is small member of the iris family in genus Sisyrinchium. The plant's natural range is in the western United states and northern Mexico. It is sometimes grown in garden settings in its native range.

<i>Penstemon arenicola</i> Plant species in the family

Penstemon arenicola, commonly known as Red Desert penstemon, is a species of plant from the Western United States. It primarily grows in Wyoming, but it also grows in small areas of Colorado and Utah. It is a short plant known for growing in sand as referenced by its scientific name.

References

  1. 1 2 3 NatureServe (2023). "Pediocactus simpsonii". Arlington, Virginia. Retrieved 13 December 2023.
  2. 1 2 3 4 5 "Pediocactus simpsonii (Engelm.) Britton & Rose". Plants of the World Online . Royal Botanic Gardens, Kew . Retrieved 6 December 2023.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Heil, Kenneth D.; Porter, J. Mark (5 November 2020). "Pediocactus simpsonii - FNA". Flora of North America. Retrieved 9 December 2023.
  4. 1 2 3 Weniger, Del (1984). Cacti of Texas and Neighboring States : A Field Guide. Austin, Texas: University of Texas Press. p. 146. ISBN   978-0-292-71085-6 . Retrieved 15 December 2023.
  5. 1 2 3 4 5 6 7 Britton, Nathaniel Lord; Rose, Joseph Nelson (1919). The Cactaceae : Descriptions and Illustrations of Plants of the Cactus Family. Washington, D.C.: The Carnegie Institution of Washington. pp. 90–91. Retrieved 8 December 2023.
  6. 1 2 3 4 5 Benson, Lyman David (1982). The Cacti of the United States and Canada. Stanford, California: Stanford University Press. p. 751-752. ISBN   978-0-8047-0863-0 . Retrieved 12 December 2023.
  7. 1 2 3 Pesman, M. Walter (Michiel Walter) (1988). Meet the Natives : A Beginner's Field Guide to Rocky Mountain Wild Flowers, Trees, and Shrubs (8th ed.). Boulder, Colorado: Pruett Pub. p. 78. ISBN   978-0-87108-731-7 . Retrieved 15 December 2023.
  8. 1 2 3 4 5 Cirigliano, Jim (2023). National Audubon Society Wildflowers of North America (1st ed.). New York: Alfred A. Knopf. p. 448. ISBN   978-0-593-31994-9.
  9. 1 2 Preston-Mafham, Ken (1994). Cacti and Succulents in Habitat. London: Cassell. p. 123. ISBN   978-0-304-34551-9 . Retrieved 16 December 2023.
  10. 1 2 3 Ingram, Stephen (2008). Popper, Marjorie; Evarts, John (eds.). Cacti, Agaves, and Yuccas of California and Nevada (1st ed.). Los Olivos, California: Cachuma Press. pp. 129–131. ISBN   978-0-9789971-0-6 . Retrieved 16 December 2023.
  11. Ackerfield, Jennifer (2015). Flora of Colorado (1st ed.). Fort Worth, Texas: BRIT Press. p. 259. ISBN   978-1-889878-45-4.
  12. Engelmann, George (1863). "Additions to the Cactus-Flora of the Territory of the United States". Transactions of the Academy of Science of Saint Louis. 2. Academy of Science of St. Louis: 197–199. Retrieved 8 December 2023.
  13. WFO (2023). "Pediocactus simpsonii (Engelm.) Britton & Rose". World Flora Online. Retrieved 8 December 2023.
  14. 1 2 3 4 Pediocactus simpsonii, USDA Natural Resources Conservation Service PLANTS Profile, 8 December 2023
  15. "Pediocactus Britton & Rose". Plants of the World Online . Royal Botanic Gardens, Kew . Retrieved 16 December 2023.
  16. "Pediocactus Britton & Rose". World Flora Online . Retrieved 16 December 2023.
  17. McDonald, Charlie. "Simpson's hedgehog cactus". Plant of the Week. U.S. Forest Service, United States Department of Agriculture. Retrieved 16 December 2023.
  18. Heil, Kenneth D.; O'Kane, Steve L.; Reeves, Linda Mary; Clifford, Arnold (2013). Flora of the Four Corners Region : Vascular Plants of the San Juan River Drainage, Arizona, Colorado, New Mexico, and Utah. St. Louis, Missouri: Missouri Botanical Garden. pp. 396–397. Retrieved 16 December 2023.
  19. Heil, Kenneth D.; Porter, J. Mark (5 November 2020). "Pediocactus - FNA". Flora of North America. Retrieved 16 December 2023.
  20. Anderson, Edward F. (2001). The Cactus family. Portland, Oregon: Timber Press. p. 559. ISBN   978-0-88192-498-5 . Retrieved 15 December 2023.
  21. Forey, Pamela (1991). Wild Flowers of North America (1st ed.). New York: Gallery Books. p. 36. ISBN   978-0-8317-6383-1 . Retrieved 16 December 2023.
  22. Leake, Dorothy Van Dyke; Leake, John Benjamin; Roeder, Marcelotte Leake (1993). Desert and mountain plants of the Southwest. Norman, Oklahoma: University of Oklahoma Press. p. 109. ISBN   978-0-8061-2489-6 . Retrieved 13 December 2023.
  23. Taylor, Ronald J. (1982). Rocky Mountain Wildflowers. Seattle, Washington: The Mountaineers. Retrieved 15 December 2023.
  24. 1 2 McGary, Jane, ed. (1996). Rock Garden Plants of North America : an anthology from the Bulletin of the North American Rock Garden Society. Portland, Oregon: Timber Press in association with the North American Rock Garden Society. pp. 199–200. ISBN   978-0-88192-343-8.
  25. Hochstätter, Fritz (2008). "The Genus Pediocactus". CactusWorld. 26 (3): 141–150. ISSN   1751-1429 . Retrieved 18 January 2024.
  26. Stevens, Jens T.; Miller, Jesse E. D.; Fornwalt, Paula J. (November 2019). "Fire severity and changing composition of forest understory plant communities". Journal of Vegetation Science. 30 (6): 1099–1109. doi:10.1111/jvs.12796.
  27. Kevan, P. G.; Gaskell, B. H. (March 1986). "The Awkward Seeds of Gonystylus macrophyllus (Thymelaeaceae) and Their Disperal by the Bat Rousettus celebensis in Sulawesi, Indonesia". Biotropica. 18 (1): 76. doi:10.2307/2388366 . Retrieved 16 December 2023.
  28. Belisle, D.; Gronborg, I. (1991). "Cacti for the North". Horticulture. 69 (8): 50.
  29. Lamb, Edgar (1975). The Illustrated Reference on Cacti & Other Succulents. Vol. 4. Poole, Dorset, UK: Blandford Press. p. 996. ISBN   978-0-7137-0691-8 . Retrieved 12 December 2023.
  30. Wagner, Frederic H. (1981). Wildlife of the Deserts. London: Winward. p. 212. ISBN   978-0-7112-0024-1 . Retrieved 15 December 2023.
  31. Love, Stephen L; Akins, Candace J (2020). "Fifth Summary of the Native Seed Germination Studies of Norman C Deno: Species With Names Beginning With Letters P and Q". Native Plants Journal. 21 (1): 87. doi:10.3368/npj.21.1.83.