Walter's choice of the local green serpentinite contrasts with the banklike severity of the windowless front and perhaps is intended to recall the masonry ends of greenhouses. The only relief to the planarity of the facade is provided by the main door in a deep splayed recess and a small datestone in the gable. Its lecture hall held such speakers as Ralph Waldo Emerson and Horace Greeley. When the Horticultural Society disbanded in 1870, the hall was adapted as a theater. It is now one of the historical society's several buildings, of which its main building was constructed in 1908 in the red brick and limestone trim of the regional Colonial Revival. Restored in 1993, the exhibits housed in the 1908 wing form a valuable introduction to the regional culture. Adjacent to the north is the modest gray stone, Colonial Revival facade of the First Church of Christ Scientist (1911) by Philadelphians Barney and Banwell.