In those early years in New York when I was a stranger in a big city, it was the companionship and later friendship which I was offered in the Linnean Society that was the most important thing in my life.

This quote is talking about the speaker’s early years in New York City. During those years, the speaker was a stranger in a new place and often felt lonely. However, they found solace in the Linnean Society, which offered them friendship and companionship. This became the most important thing in the speaker’s life, providing a sense of comfort and security during a difficult time.