EVERYDAY SCIENCE

Detailed explanation-1: -Amphiphloic Siphonostele: In this type of stele the center is occupied by the pith. Xylem is surrounded on both the external & internal sides by a ring of phloem. e.g., Marsilea rhizome.

Detailed explanation-2: -In submerged plants the petiole is a long and flexible structure and the lamina floats over the surface of water but in muddy or marshy plants the petiole of the leaf is short and rigid with short lamina spreading in the air. The lamina consists of 4 leaflets (pinnae) which are present at the apex of petiole.

Detailed explanation-3: -Mixed protostele Xylem is divided into several units or groups. Each xylem units are scatteredly arranged inside the ground mass of phloem. Example: Lycopodium cernuum.

Detailed explanation-4: -Marsilea is a heterosporous fern. It produces two types of spores i.e., the microspores and the megaspores. The microspores and megaspores are produced in microsporangia and megasporangia, respectively, and the sporangia are enclosed in special bean-shaped structures called sporocarps.