... animals, etc) producing much fruit or many flowers or offspring （指动植物等）多产的, 多育的 *prolific growth 多产植物. 2 (of a writer, an artist, etc) producing many works （指作家、艺术家等）多创作的 ..
My guess is that the most profitable (and prolific) class action firms regularly engage in activity that may limit their potential growth and preclude mergers with other firms.