Mentored in botany by Henry David Thoreau, whom he accompanied on an expedition to Minnesota, Mann took classes in zoology with Louis Agassiz and assisted William Tufts Brigham botanize the Hawaiian Islands.
After completing his first year of college at Antioch in 1859, Mann spent several weeks in the Boston home of Samuel Gridley and Julia Ward Howe.
[2] Upon his father's death due to typhoid fever in 1859, the family returned to their mother's home-state of Massachusetts and the village of Concord, renting for a time the home of Mann's aunt and uncle, Nathaniel and Sophia Hawthorne, known as The Wayside.
[5] That fall, Mann began studies at Lawrence Scientific School at Harvard College,[6] taking lessons in zoology with Louis Agassiz.
[8] In 1864, Horace Mann accompanied William Tufts Brigham on a botanical survey of the Hawaiian Islands, where they discovered more than 100 plant taxa new to science, including Cyanea lobata or the genera Platydesma and Alsinidendron.