Morphology of Flowering Plants

In axile placentation the placenta is axial and the ovules are attached to it in a multilocular ovary, as in china rose, tomato and lemon.
Marigold (and sunflower) have basal placentation: a single ovule attached at the base of a unilocular ovary.
$Argemone$ (and mustard) have parietal placentation: ovules on the inner wall of the ovary.
$Dianthus$ (and primrose) have free central placentation: ovules on a central axis without septa.
Hence the example of axile placentation is lemon.

The formula describes an actinomorphic ($\oplus$), bisexual flower with five united sepals $K_{(5)}$, five united petals $C_{(5)}$, five epipetalous stamens $A_5$ and a bicarpellary, syncarpous, superior ovary $\underline{G}_{(2)}$.
These are the characters of the family Solanaceae, to which tobacco, tomato, potato, brinjal, chilli and petunia belong.
Tulip belongs to Liliaceae: $\oplus$ ⚥ $P_{3+3}A_{3+3}\underline{G}_{(3)}$
Soybean and sunnhemp belong to Fabaceae: % ⚥ $K_{(5)}C_{1+2+(2)}A_{(9)+1}\underline{G}_1$
Hence the floral formula is that of tobacco.