TROPOTAXIS

ai ar as at ax is it oi op or os ox pa pi si so ta ti to xi

air ais ait apo apt ars art asp att its oar oat oot ops opt ora ors ort oxo par pas pat pax pia pis pit pix poi poo pot pox pro psi pst rai rap ras rat rax ria rip rot sap sat sax sip sir sit six sop sot sox spa sri tao tap tar tas tat tax tip tis tit too top tor tot xis

airs airt aits apos arts atop axis iota oars oast oats oops oots opts orts osar otto pair pars part past pats pias piso pita pits pois poor poos port post pots prao prat proa pros rais raps rapt rasp rato rats rias riot rips root rota roti roto rots sari sati soap soar soot sora sori sort spar spat spit spot star stat stir stoa stop stot taos taps taro tarp tars tart tats taxi tips tiro tits toit toot topi topo tops tora tori toro tors tort tost tots trap trio trip trop trot tsar