You might like to consider the pear tree that Janie lies under in Chapter Two and the image of nature it presents and how this seems to govern her quest for self-identity. Let us consider how this important part of Janie's life is described in this excellent book:
She was stretched on her back beneath the pear tree soaking in the alto chant of the visiting bees, the gold of the sun and the panting breath of the breeze when the inaudible voice of it all came to her. She saw a dust-bearing bee sink into the sanctum of a bloom; the thousand sister-calyxes arch to meet the love embrace and the ecstatic shiver of the tree from root to tiniest branch creaming in every blossom and frothing with delight. So this was a marriage! She had been summoned to behold a revelation.
What she sees in the way that the bee unites itself with the blossom is a symbol of the unity and harmony present in nature, which is also very sexual in its being. In a sense, Janie, throughout the rest of this book, tries to achieve this ideal in her own life.
In the same way, the symbol of the horizon and the way that it represents the mystery of nature with which Janie yearns to connect, is something that occurs again and again throughout the pages of this novel. Note the way that at the end of the novel we are told that Janie pulls in "her horizon like a great fish-net." This clearly points towards the final consummation of Janie's desire to be connected with nature that has been expressed throughout the entire novel.