pulvinus
pul.vi.nus \.p*l-'vi--n*s, -'ve--\ \-'vi--.ni-, -'ve--(.)ne-\ n or pul.vi.ni [NL, fr. L, cushion] pl : a mass of large thin-walled cells surrounding a vascular strand at the b ase of a petiole or petiolule and functioning in turgor movements