Concept: This question tests your knowledge of floral morphology, specifically aestivation and placentation, in plants belonging to the family Fabaceae (Leguminosae), particularly the subfamilies Caesalpinioideae and Mimosoideae.

Why (C) is correct: Both Cassia (subfamily Caesalpinioideae) and Caesalpinia (subfamily Caesalpinioideae) exhibit imbricate aestivation. In imbricate aestivation, one petal is completely internal, one is completely external, and the remaining petals have one margin internal and one margin external, without a definite pattern of overlap.

Why other options are wrong:

(A) Both have twisted aestivation: Twisted aestivation is characteristic of plants like cotton, china rose, and lady's finger, not Cassia or Caesalpinia.

(B) Both have axile placentation: Axile placentation is found in plants like china rose, tomato, and lemon, where ovules are attached to the central axis in a multilocular ovary. Legumes (including Cassia and Caesalpinia) typically have marginal placentation.

(D) Both have parietal placentation: Parietal placentation is seen in mustard and Argemone, where ovules develop on the inner wall of the ovary or on peripheral part. Legumes have marginal placentation.

Common Mistake: Students often confuse the different types of aestivation (valvate, twisted, imbricate, vexillary) and placentation (marginal, axile, parietal, free central, basal).

NEET Tip / Mnemonic: For aestivation, remember: Valvate (Calotropis), Twisted (China rose, Lady's finger, Cotton), Imbricate (Cassia, Caesalpinia), Vexillary (Pea, Bean). For placentation, remember: Marginal (Pea), Axile (China rose, Tomato, Lemon), Parietal (Mustard, Argemone), Free central (Dianthus, Primrose), Basal (Sunflower, Marigold).

Correct Answer: (C)