When the leaves were well out on the trees Helen held an Observation Class one afternoon, in front of the cave.
"How many members of this handsome and intelligent Club know what leaves are for?" she inquired.
"As representing in a high degree both the qualities you mention, Madam President," returned Tom, with a bow, "I take upon myself the duty of replying that perhaps you and Roger do because you've studied botany, and maybe Margaret and James do because they've had a garden, and it's possible that the Ethels and Dorothy do inasmuch as they've had the great benefit of your acquaintance, but that Della and I don't know the very first thing about leaves except that spinach and lettuce are good to eat."
"Take a good, full breath after that long sentence," advised James. "Go ahead, Helen. I don't know much about leaves except to recognize them when I see them."
"Do you know what they're for?" demanded Helen, once again.
"I can guess," answered Margaret. "Doesn't the plant breathe and eat through them?"
"It does exactly that. It takes up food from water and from the soil by its roots and it gets food and water from the air by its leaves."
"Sort of a slender diet," remarked Roger, who was blessed with a hearty appetite.
"The leaves give it a lot of food. I was reading in a book on botany the other day that the elm tree in Cambridge, Massachusetts, under which Washington reviewed his army during the Revolution was calculated to have about seven million leaves and that they gave it a surface of about five acres. That's quite a surface to eat with!"
"If each one of you will pick a leaf you'll have in your hand an illustration of what I say," suggested Helen.
They all provided themselves with leaves, picking them from the plants and shrubs and trees around them, except Ethel Blue, who already had a lily of the valley leaf with some flowers pinned to her blouse.
"When a leaf has everything that belongs to it it has a little stalk of its own that is called a _petiole_; and at the foot of the petiole it has two tiny leaflets called _stipules_, and it has what we usually speak of as 'the leaf' which is really the _blade_."
They all noted these parts either on their own leaves or their neighbors', for some of their specimens came from plants that had transformed their parts.