Geissoloma marginatum
| Geissoloma marginatum | ||||||||||||
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Geissoloma marginatum |
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| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Geissolomataceae | ||||||||||||
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| Scientific name of the genus | ||||||||||||
| Geissoloma | ||||||||||||
| Lindl. ex Kunth | ||||||||||||
| Scientific name of the species | ||||||||||||
| Geissoloma marginatum | ||||||||||||
| ( L. ) Kunth |
Geissoloma marginatum is an evergreen shrub from the Cape Province . It is the only species of the genus Geissoloma , which in turn alone forms the plant family of the Geissolomataceae within the order Crossosomatales .
features
Habit and leaves
Geissoloma marginatum is a small, xerophytic , but not succulent shrub with evergreen leaves . The young trunks are slightly square. A cork cambium is available. There is no internal phloem . The secondary growth in thickness takes place via a normal cambium ring.
The leaves are opposite, leathery and sessile or with only a short petiole. The leaves are simple with an undivided leaf blade . The leaf veins are pinnate. The stipules sit on the petiole (intrapetiolar), but are not fused. You are small. The leaves have a mucous epidermis . The stomata have no secondary cells (they are anomocytic). The mesophyll is free from sklerenchymatic idioblasts . However, it contains calcium oxalate crystals in drusen form .
blossoms
The flowers are solitary at the end of short axillary branches. There are six bracts (perennial, in three pairs) on the flower stalk . The flowers are four-fold with four leaf circles. A flower base (hypanthium) is missing.
The inflorescence consists of only a four-fold leaf circle and is interpreted as a calyx. The four leaves are red to pink, fused at the base. The free lobes, however, are significantly longer than the tube. The sepals are persistent and overlapping.
The Androeceum consists of two circles (diplostemon) with four stamens each . They are free or start at the base of the chalice (adnat). The two circles are clearly different in that the stamens opposite the calyx are significantly longer. All stamens are fertile. The stamens are slender, the anthers are ellipsoidal and open with longitudinal slits. The pollen is distributed as single grains. He is a tricolor.
The gynoecium consists of four fused carpels that form a vierfächerigen, upper ovary. The four styluses are free at the bottom and grown together at the top. There are also four scars . The placentation is central angled. There are two anatropic ovules per compartment with two integuments (bitegmic). The outer integument contributes to the formation of the micropyle . The polar nuclei fuse together before fertilization. There are three antipodes that do not multiply and perish.
fruit
The fruit is a loculicidal capsule fruit with four seeds. These have an endosperm and a well-developed embryo with two fleshy cotyledons. The embryo is central and straight. The seed coat is shiny.
distribution
The species is restricted to the Cape Province in South Africa . The plants are aluminum accumulators.
Systematics
The systematic position of the plant is sometimes handled differently:
Cronquist the genus in which Celastrales found Tachtadschjan other hand, in the Ericanae (see takhtajan system ).
From the APG website, the genus is placed in the order Crossosomatales . The Geissolomataceae form the sister taxon of the group from Ixerbaceae and Strasburgeriaceae .
Sources and further information
The article is based primarily on the following two web links:
- Watson, L., and Dallwitz, MJ 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 1st June 2007
- Geissolomataceae on the APG website
literature
- EL Stephens: The Embryo-sac and Embryo of Geissoloma marginata. In: New Phytologist. Vol. 8, No. 9/10, 1909, ISSN 0028-646X , pp. 345-348, doi : 10.1111 / j.1469-8137.1909.tb05540.x
- Sherwin Carlquist: Leaf Anatomy of Geissolomataceae and Myrothamnaceae as a Possible Indicator of Relationship to Bruniaceae. In: Bulletin of the Torrey Botanical Club. Vol. 117, No. 4, 1990, ISSN 0040-9618 , pp. 420-428, doi : 10.2307 / 2996839 .
