In Bradbury's "Fahrenheit 451." the second time Montag meets Clarisse she is holding something in her hand. He inquires as to what she is holding and she replies that it is a dandelion. She proceeds to rub under her chin with the dandelion and asks Montag if it is yellow. If it is she is in love. He replies that it is yellow. She says great let's do yours now.
" 'Here,' Before he could move she had put the dandelion under his chin. He drew back and she laughed. 'Hold still!'
She peered under his chin and frowned.
'Well?' he said.
'What a shame,' she said. 'You're not in love with anyone.'
'Yes, I am!'
'It doesn't show.'"
They go back and forth with Montag insisting he is very much in love and Clarisse saying that it doesn't appear so, and then Montag makes the excuse that "she must have used up all the yellow."
the love test with the dandelion and rubed it under his chin