Geissoloma

Geissoloma marginatum is an evergreen shrub from the Cape Province. It is the only species of the genus Geissoloma, which in turn forms alone the plant family of Geissolomataceae within the order Crossosomatales.

• 4.1 Literature
• 4.2 External links

Features

Habitus and sheets

Geissoloma marginatum is a small, xerophytic, but not succulent shrub with evergreen leaves. The young stems are slightly rectangular. A cork cambium is present. There are no internal phloem. The Secondary growth in thickness is via a normal Kambiumring.

The leaves are opposite, leathery and sitting or with only a short petiole. The leaves are simple with an undivided leaf blade. The leaf veins are fiederförmig. The stipules sit on the petiole ( intrapetiolar ), but are not fused. They are small. The leaves have a schleimhältige epidermis. The stomata have no side cells (they are anomocytisch ). The mesophyll is free of sclerenchymatous idioblasts. However, it contains calcium oxalate crystals in geodes form.

Flowers

The flowers appear singly at the end of short axillary branches. At the pedicel bracts are six ( persistent, in three pairs ). The flowers are cruciform with four leaf circles. A flower base ( hypanthium ) is missing.

The perianth consists of only a fourfold blade circular and is interpreted as a chalice. The four petals are red to pink, united at the base. However, the free Lappe are significantly longer than the tube. The sepals are persistent and overlapping.

Androecium consists of the two circles ( diplostemon ) of four stamens. They are free or set at the base of the chalice at ( adnat ). The two circles are significantly different by the the cup opposite stamens are much longer. All stamens are fertile. The stamens are slender, the anthers are ellipsoidal and open with longitudinal slots. The pollen is used as single grains. He is tricolpate.

The gynoecium consists of four carpels that form a vierfächerigen, superior ovaries. The four pen have grown down freely and above. There are also four scars. The placentation is central angle constantly. Per compartment there are two ovules with two integuments anatrope ( bitegmisch ). The outer integument contributes to formation of the micropyle. The polar nuclei fuse prior to fertilization. There are three antipodes, which do not reproduce, and perish.

Fruits

The fruit is a capsule lokulizide fruit with four seeds. These have an endosperm and a well-trained embryo with two fleshy cotyledons. The embryo is centrally located and just. The seed coat is shiny.

Dissemination

The species is restricted to the Cape Province in South Africa. The plants are aluminum accumulators.

System

The systematic position of the plant is handled partly different:

Cronquist, the genus has placed in the Celastrales, Tachtadschjan contrast, in the Ericanae (see classification of angiosperms after Tachtadschjan ).

From the APG site, 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 mainly based on the following two links:

• Watson, L., and Dallwitz, M. J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 1st June 2007
• Geissolomataceae on the APG website