line ▁clear ances , ▁road ▁and ▁rail road ▁sides , ▁vac ant ▁lots , ▁and ▁waste ▁areas . ▁It ▁is ▁most ▁common ▁in ▁de grad ed ▁and ▁dist urbed ▁habit ats , ▁but ▁also ▁may ▁be ▁found ▁in ▁rich ▁and ▁diverse , ▁high - quality ▁habit ats . ▁ ▁Us es ▁L act uca ▁canad ensis ▁contains ▁la ct uc arium , ▁which ▁is ▁the ▁mil ky ▁sap ▁( white ▁late x ) ▁that ▁flows ▁through ▁the ▁stem , ▁leaves , ▁and ▁roots ▁of ▁the ▁plant . ▁It ▁is ▁used ▁as ▁a ▁medic inal ▁her b ▁when ▁d ried ▁after ▁contact ▁with ▁air . ▁A ▁surv ival ist ▁publication , ▁The ▁Lost ▁W ays , ▁states ▁that ▁its ▁fresh ▁leaves ▁may ▁be ▁use ▁to ▁create ▁a ▁solution ▁that ▁may ▁act ▁as ▁an ▁anal ges ic ▁and ▁may ▁be ▁stored ▁for ▁later ▁use . ▁It ▁may ▁be ▁used ▁as ▁medic inal ▁treat ments ▁for ▁its ▁an ody ne , ▁ant isp as mod ic , ▁dig est ive , ▁di ure t ic , ▁hyp not ic , ▁n arc otic , ▁and ▁sed ative ▁properties . ▁Con cent r ations ▁of ▁la ct uc arium ▁are ▁low ▁in ▁young ▁plants , ▁but ▁increase ▁in ▁older ▁plants , ▁occurr ing ▁highest ▁when ▁in ▁blo oming ▁period . ▁S ap ▁may ▁be ▁applied ▁to ▁skin ▁in ▁use ▁for ▁treatment ▁of ▁external ▁w arts . ▁It ▁has ▁been ▁seen ▁as ▁valuable ▁in ▁treatment ▁as ▁a ▁rem edy ▁for ▁ins om nia ▁and ▁mus cular ▁ar th