Complex sentence: For the MBG, a snowball effect occurred in the tropics; orchid collecting began there in earnest and over the next 13 years of its operation, orchids from the Tropical Station would appreciably augment the collection of the parent garden in St. Louis.
Split into simpler sentences: For the MBG, a snowball effect occurred in the tropics; orchid collecting began there in earnest. Over the next 13 years of its operation, orchids from the Tropical Station would appreciably augment the collection of the parent garden in St. Louis.