In the spring of 1849 Harvey accepted an invitation from the Smithsonian Institution and Harvard University to deliver twelve lectures on botany at the Lowell Institute at Boston, and others at Washington. The subject he chose for the Boston course was a comprehensive survey of the plant-world, from the point of view of the "progressive organization of the vegetable entity." The cryptogams had a place of honour, four lectures being devoted to Algae: it is interesting to note that the Fungi, which he designates "the most aristocratic of Crypts--_fruges consumere nati_," he placed immediately below the Flowering Plants, for reasons which, no doubt, he gave in his discourses. He sailed from Liverpool in July. Ocean traffic had been revolutionized since his last voyage from the Cape; instead of a dawdling sailing-ship, a steamer transported him in ten days to Nova Scotia; and with some of the old excitement with which he had started on his first climb up Table Mountain, he rambled away into the dark spruce woods, through the rich undergrowth of Kalmias, Ledums and Andromedas, with Sarracenias and Orchids rising from among the Sphagnums in the damper spots. He dredged and shore-collected also, but the seaweed flora was not rich. Thence he passed to New York, which he describes as like twenty Birkenheads and a dozen Liverpools, with slices from London and Paris, all huddled together, and painted bright red, with green windows. He visited Niagara and Quebec, and then travelled to Boston, where he was welcomed by Asa Gray, who was his host during his stay. The lectures were well attended, and Harvey seems to have been satisfied with them and with the reception which they received; a popular lecture on seaweeds at the Franklin Institute at Providence was largely attended. These discourses, and the introductions and conversations that ensued, had more than a passing interest, as recruits were enrolled for alga-collecting, who subsequently supplied valuable material for his work on North American seaweeds. He saw all that was best of scientific society in Boston and New York, and met many of the great men of that generation--Agassiz, Bailey, Dana, Longfellow, Leidy, Pickering, Prescott, Silliman, Daniel Webster, Oliver Wendell Holmes. Having fulfilled his engagements and revisited the family of his late brother Jacob in New York, he turned his face southward in January for a collecting tour along the Atlantic sea-board.