Semi-desert, foothills, montane. Springs, streams. Summer.
Negro Bill Canyon, April 1, 2004.

Watercress was introduced from Europe and is now quite at home throughout the United States -- even in grocery stores.  Its tiny white flowers (not shown) float on stems just above the water.  The plant has a pleasant peppery taste but it can be unsafe to consume this plant in the wild because of contaminated water.

"Nasturtium" is apparently from the Latin "nasus tortus", "twisted nose", referring to the contortions human noses go through because of the sharp, peppery smell of Nasturtium officinale seeds.  "Officinale" is Latin for "of the shops", basically meaning that it has at some time been accepted as an official herb/drug. 

Semi-desert, foothills, montane. Springs, streams. Summer.
Negro Bill Canyon, April 1, 2004.

In 1753 Linnaeus named this species Sisymbrium nasturtium-aquaticum and in 1812 the botanist Robert Brown renamed it Nasturtium officinale.