Category: BOTANY(I Year VIDEO)

Oscillatoria is found in rain water of pools, ponds, rivers, streams, lakes and in polluted water. Some of the species of Oscillatoria are plank tonic, some are found in hot water springs e.g O. terebriformis, and some species of Oscillatoria are found in saline waters. e.g. O. limosa. Oscillatoria in unbranched and filamentous. The trichome consists of cells which are arranged in uniseriate fashion. Oscillatoria species show Gaidukov phenomenon. Species of Oscillatoria can assume different shades when they are provided with light of different wavelengths. The trichome shows gliding movement as well as oscilllatory movement. During vegetative growth of the trichome, some cells of the trichome are filled with mucilage and become dead. These cells are called necridia. Thus Oscillatoria reproduces by the formation of Hormogonia and by fragmentation.

Cycas is an evergreen , palm like small tree. It grows in xerophytic habitats. The sporophytic plant body of Cycas is differentiated into roots, stem and leaves. The roots are of two types : Normal tap roots and coralloid roots. The leaves are also of two types i.e. dimorphic . The assimilatory leaves or foliage leaves and Scale leaves . The asexual reproduction takes place by the formation of sporangia and spores . The sporangia are arranged on the lower side of the microsporophyll in definite groups called sori. Sexual reproduction occurs by the formation of antheridia and archegonia.