What type of leaf arrangement is found in Selaginella?
The leaves are arranged in four vertical rows. Leaves present in pairs. The larger leaf of each pair is attached toward, the ventral side of the stem and the smaller leaf towards the dorsal side. The leaves bearing sporangia in their axils are called sporophylls.
How are the leaves of Selaginella?
Selaginella species are creeping or ascendant plants with simple, scale-like leaves (microphylls) on branching stems from which roots also arise. The stems are aerial, horizontally creeping on the substratum (as in Selaginella kraussiana), sub-erect (Selaginella trachyphylla) or erect (as in Selaginella erythropus).
What is the structure of selaginella?
Selaginella produces two types of spores—megaspores and microspores. The dimorphic condition of the spores is known as heterospory. In between the sporophyll and sporangium is present a small membranous structure known as ligule i.e., the sporophyll is similar to a vegetative leaf.
What type of vascular arrangement is characteristic of the stem of selaginella?
S. wallacei stems are characterized by a simple stele consisting of a single vascular segment (Fig. 2d).
How are the xylem and phloem arranged in Selaginella sp?
Thus, the central stele is separated from the cortex by large air spaces. Regardless of the stelar organisation, the primary xylem is exarch in development and the metaxylem consists primarily of tracheids with scalariform pittings. The phloem of Selaginella consists of sieve cells and parenchyma.
How are the xylem and phloem arranged in Selaginella?
e. Polystele: Generally in a protostele, the stem has a single stele in the centre. But in Selaginella, the stem axis has several steles in parallel arrangement (di-stelic or polystelic). Each stele is a protostele with xylem core surrounded by phloem with pericycle and endodermis.
Which structure is developed from Microspore of the Selaginella?
The microspores on germination give rise to male prothalli and megaspores to the female prothalli. Structure of Mature Archegonium: The archegonium is a short flask shaped structure embedded in female gametophytic tissue (Fig.
What is present in Selaginella stem?
Note: The stem of Selaginella is shaped like a vascular stele which is protostele. Xylem is available in the middle and is encircled by phloem and phloem is encircled by pericycle. Pith is missing. Trabeculae are available which are tube loved structures and are adjusted endodermal cells with casparian strips.
What are Rhizophores in Selaginella?
feature of Selaginella is the rhizophore, a proplike structure that originates at a point of branching and that forks dichotomously after making contact with the soil or a hard surface. Rhizophores are most readily seen in clambering species.
What is Selaginella Strobilus?
The genus Selaginella is classified in the division Lycophyta, which includes the numerous plants commonly known as clubmosses and spike mosses. Similar to their close relatives, Selaginella plants develop strobili, spike-like reproductive organs that form on fertile branches.
What is rhizophore and its function?
function in lycophytes feature of Selaginella is the rhizophore, a proplike structure that originates at a point of branching and that forks dichotomously after making contact with the soil or a hard surface. Rhizophores are most readily seen in clambering species.
What are the external features of a Selaginella?
Observe the external features of the plant, and arrangement, types and shape of leaf, ligule, rhizophore and roots. 1. Plant body is sporophytic and the sporophyte is evergreen and perennial. 2. Most of the species are prostrate but Selaginella trachyphylla is sub-erect and S.erythropus is erect (Fig. 208).
What are the names of the two genera of Selaginella?
Most of the species are perennials. on the basis of structure of stem and arrangement of leaves, Selaginella is divided into two sub genera namely Homoeophyllum and Heterophyllum. Homeophyllum include species with erect stem and spirally arranged leaves.
How are Selaginella and homeophyllum classified as epiphytes?
S. oregana is an epiphyte. Most of the species are perennials. on the basis of structure of stem and arrangement of leaves, Selaginella is divided into two sub genera namely Homoeophyllum and Heterophyllum. Homeophyllum include species with erect stem and spirally arranged leaves.
What kind of rhizophore does a Selaginella have?
Besides, some species also have rhizophore (Fig.7.46A). Hieronymus (1902) divided the genus Selaginella into two sub-genera viz., Homoeophyllum and Heterophyllum on the basis of general structure of the plant body (Table 7.4). The stem is generally erect and radially conÂstructed in the subgenus Homoeophyllum.