Etymology: The genus name "Echinopsis" derives from the Greek word “echinos (εχινος) ” meaning "porcupine or hedgehog", "sea urchin” and the word "opsis (οφις)" meaning “appearance, seeing, like” referring to the spines that cover the plant as it looks like a rolled up hedgehog.(The genus name implies: "like a porcupine")
The species name “spachiana” is named in honour of the Alsatian botanist "Edouard Spach (1801-1879)"

Another flowering plant .
Photo and © copyright by Andrea B. (Bologna, Italy)
http://www.cactusfriends.com/Andrea/index.html 

Morphology (Identifying Characteristics):
Habit: Multi-stemmed columnar cactus
Stem: Stem upright, at first simple, later profusely branching at the base; branches ascending parallel with the main stem. Up to about 2 mt, but usually smaller, 5 to 6 cm. in diameter, columnar; ribs 10 to 15, obtuse, rounded;
Areoles : About 1 cm. apart, large, covered with curly yellow wool, turning white or grey as they age;
Spines: Radial spines 8 to 10,  6 mm to 1 cm. long, spreading, stiff, sharp, amber-yellow to brown; central 1 to 3 yellowish centrals, 12 mm long, stronger and longer than the radials; all the spines later becoming grey.
Flower: Nocturnal,  white, about 20 cm. long and 15 cm. in diameter lasting about 24 hours from one sunset to the following one.  Blooming time is in late spring.