After dipping in the fourth quarter of 2006, greentech investment has turned back up. According to the Cleantech Venture Network, North American investment for the first quarter of 2007 - the latest available - totaled $731 million, up 19 percent over the last quarter in 2006 and 42 percent over the first quarter of last year. Of course, investment was still 21.7 percent short of last year's third-quarter high of $933 million. But with three quarters of numbers left to compile, greentech insiders hope 2007 investments will still catch up with those of 2006, the year Ira Ehrenpreis, a general partner with venture-capital firm Technology Partners, dubbed the "coming-of-age" year for greentech.