Practice question

Selaginella represents crucial evolutionary transition among vascular plants as heterosporous lycophyte producing morphologically distinct dimorphic spores within same strobilus but separate sporangia: numerous small microspores developing into reduced male gametophytes releasing flagellated sperm, and large nutrient-rich megaspores containing stored reserves forming female gametophytes with archegonia. While most lycopods like Lycopodium are homosporous with bisexual free-living gametophytes, heterospory in Selaginella shows endosporic development, retention of megaspore within sporangium temporarily, and intrasporangial nutrition representing precursors to seed habit without forming integument. This structural framework illustrates phylogenetic relationships and adaptive significance highlighted in competitive examinations focusing on comparative plant morphology and systematics.