Jacobsenia
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Jacobsenia is a genus of plants fromthe afternoon flower family (Aizoaceae). The botanical name of the genus honors the German succulent specialist and former technical director of the Botanical Garden in Kiel Hermann Jacobsen .
description
The species of the genus Jacobsenia grow shrubby with heights of up to 50 centimeters or almost compact and are then up to 15 centimeters high. Young plants grow like a lawn. Adult plants have upright shoots with elongated internodes and short side shoots or they have a more or less compact habit without any recognizable separation into short and long shoots. Every year 2 (rarely 4) pairs of leaves are formed, which are fused together for about a fifth of their length. The upright or spreading, up to 7 centimeters long leaves are somewhat finger-shaped, usually somewhat curved, sometimes a little flattened at the top and sometimes a little keeled at the bottom. Their diameter is up to 1 centimeter. The thickened outer cell walls of the epidermis contain large, elliptical to somewhat round bladder cells .
The individual flowers appear from the overgrown part of the second pair of leaves of the year, reach a diameter of up to 8 centimeters and sit at the end on a 1 to 7 centimeter long flower stalk . There are 5 to 6 sepals available. The petals are white, light yellow or very rarely red, with the inner petals being shorter than the outer. Thread-like staminodes are usually missing or only very few are present. The stamens are colored white or yellow.
The capsule fruits are 5- to 16-faceted, reach a diameter of 5 to 17 centimeters and are similar to the fruits of the genus Mitrophyllum . There is a fan cover, but the closure body is missing. The brown to light brown, tiny papillary seeds are about 0.7 millimeters long and 0.5 millimeters wide.
The chromosome number is .
Systematics and distribution
The distribution area of the genus Jacobsenia extends from the southwest of the Namaqualand in the South African province of Northern Cape to the places Vanrhynsdorp and Vredendal in the province of Western Cape . The plants grow on rocky soils, sometimes on slate reefs or in loamy, very salty sand. The annual rainfall is 100 to 200 millimeters, with the majority falling in winter.
The first description was published in 1954 by Harriet Margaret Louisa Bolus and Gustav Schwantes . The holotype is Jacobsenia kolbei . According to Heidrun Hartmann (* 1942) the genus Jacobsenia includes the following species:
- Jacobsenia hallii L. Bolus
- Jacobsenia kolbei (L.Bolus) L.Bolus & Schwantes
- Jacobsenia vaginata (L. Bolus) Ihlenf.
proof
literature
- Heidrun EK Hartmann (eds.): Illustrated Handbook of Succulent Plants: Aizoaceae F-Z . Springer, Berlin, Heidelberg, New York 2001, ISBN 3-540-41723-0 , pp. 65-67 .
- Gideon Smith et al. a. (Ed.): Mesembs of the World: Illustrated Guide to a Remarkable Succulent Group . Briza Publications, 1998, ISBN 1-875093-13-3 , pp. 236-237 .
Individual evidence
- ↑ Louisa Bolus, Gustav Schwantes: Jacobsenia L.Bol. et Schwant. gen. nov. In: Cacti and other succulents . Volume 3, 1954, pp. 69-71.
- ↑ Heidrun EK Hartmann: Illustrated Handbook of Succulent Plants: Aizoaceae F – Z. Springer, Berlin, Heidelberg, New York 2001, p. 66.
