Plug Power Inc. (NASDAQ: PLUG) saw short interest rise by 0.9% to 33.82 million shares. Days to cover rose from four to eight and about 15% of the company's shares were short. In the latter weeks of October, the share price slipped by about 0.7%. The stock's 52-week range is $0.83 to $3.21, and shares closed Thursday at $2.51, down more than 13% for the day.