sentences:  However, as in 1753 the Società Botanica was formed, the garden's focus turned to "experimental agriculture" and its layout was revised accordingly.The garden grounds opened to the public in the mid-19th century, at about the same time that its glass houses (1694 m²) were constructed.Today the garden contains some 9,000 plant specimens laid out in a roughly square site surrounded by walls, crossed by a grid of walkways, and with a central fountain.