Complex sentence: In the spring of 1907 it was decided that a natural sciences building should be conceived rather than an additional agricultural building as the trustees were concerned about safely storing the college's growing collections.
Split into simpler sentences: In the spring of 1907 it was decided that a natural sciences building should be conceived rather than an additional agricultural building. The plans in place at the time were further developed and the trustees were concerned about safely storing the college's growing collections.