The main plant body of pteridophytes is diploid sporophyte, differentiated into true roots, stem and leaves. Pteridophytes are vascular plants in which vascular tissues (xylem and phloem) are present. In xylem, true vessels are absent. In phloem, companion cells and sieve tubes are absent. Instead, sieve cells are present. Meiospores are formed inside sporangia by sporic meiosis. Spores may be similar (homosporous) as in majority of pteridophytes e.g., Pteris, Adiantum. A few pteridophytes are heterosporous, i.e., with two types of spores, microspores and megaspores, e.g., Selaginella, Salvinia, Marsilea.