There was also a collection of brakes that Rollo made, which the children liked to look over very much. There is a great variety in the forms of brakes, or ferns, and yet they are all regular and beautiful, and are so flat that they are easily pressed and preserved. But of all the botanical collections which were formed and deposited in this museum, one of the prettiest was a little collection of _petals_, which Rollo's mother made. Petals are the colored leaves of flowers,--those which form the flower itself. Sometimes the flower cannot be pressed very well whole, and yet, if you take off one of its petals, you find that that will press very easily, and preserve its color finely. So Rollo's mother, every day, when she saw a flower, would put one of the leaves into a book, and after a time she had a large collection,--red, and white, and blue, and yellow, and brown, in fact, of almost every color. Then she made a little book of white paper, because she thought the colors and forms of these delicate petals would appear to better advantage on a smooth, white ground. She then made a selection from all which she had preserved, and arranged them upon the pages of her little book, so as to bring a great variety both of form and color upon a page; and yet forms and colors so selected that all that was upon one page should be in keeping and harmony. But it was not merely the botanical collections in the museum which interested the children. They had some philosophical apparatus. There was what the boys called a sucker, which consisted of a round piece of sole leather, about as big as a dollar, with a string put through the middle, and a stop-knot in the end of it, to keep the string from coming entirely through; then, when the leather was wet, the boys could just pat it down upon a smooth stone, and then lift the stone by the string; the sucker appearing to stick to the stone very closely. Rollo did not understand how the sucker could lift so well; his father said it was by the pressure of the atmosphere, but in a way that Rollo was not old enough to understand.