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!"

"Some mouth!" commented Roger.

"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.

"What is the blade of your leaf made of?" Helen asked Ethel Brown.

"Green stuff with a sort of framework inside," answered Ethel, scrutinizing the specimen in her hand.

"What are the characteristics of the framework?"

"It has big bones and little ones," cried Della.

"Good for Delila! The big bones are called ribs and the fine ones are called veins. Now, will you please all hold up your leaves so we can all see each other's. What is the difference in the veining between Ethel Brown's oak leaf and Ethel Blue's lily of the valley leaf?"

After an instant's inspection Ethel Blue said, "The ribs and veins on my leaf all run the same way, and in the oak leaf they run every which way."

"Right," approved Helen again. "The lily of the valley leaf is parallel-veined and the oak leaf is net-veined. Can each one of you decide what your own leaf is?"

"I have a blade of grass; it's parallel veined," Roger determined. All the others had net veined specimens, but they remembered that iris and flag and corn and bear-grass—yucca—all were parallel.

"Yours are nearly all netted because there are more net-veined leaves than the other kind," Helen told them. "Now, there are two kinds of parallel veining and two kinds of net veining," she went on. "All the parallel veins that you've spoken of are like Ethel Blue's lily of the valley leaf—the ribs run from the stem to the tip—but there's another kind of parallel veining that you see in the pickerel weed that's growing down there in the brook; in that the veins run parallel from a strong midrib to the edge of the leaf."

James made a rush down to the brook and came back with a leaf of the pickerel weed and they handed it about and compared it with the lily of the valley leaf.

"Look at Ethel Brown's oak leaf," Helen continued. "Do you see it has a big midrib and the other veins run out from it 'every which way' as Ethel Blue said, making a net? Doesn't it remind you of a feather?"

They all agreed that it did, and they passed around Margaret's hat which had a quill stuck in the band, and compared it with the oak leaf.

"That kind of veining is called pinnate veining from a Latin word that means 'feather,'" explained Helen. "The other kind of net veining is that of the maple leaf."

Tom and Dorothy both had maple leaves and they held them up for general observation.

"How is it different from the oak veining?" quizzed Helen.

"The maple is a little like the palm of your hand with the fingers running out," offered Ethel Brown.

"That's it exactly. There are several big ribs starting at the same place instead of one midrib. Then the netting connects all these spreading ribs. That is called palmate veining because it's like the palm of your hand."

"Or the web foot of a duck," suggested Dorothy.

"I should think all the leaves that have a feather-shaped framework would be long and all the palm-shaped ones would be fat," guessed Della.

"They are, and they have been given names descriptive of their shape. The narrowest kind, with the same width all the way, is called 'linear.'"

"Because it's a line—more or less," cried James.

"The next wider, has a point and is called 'lance-shaped.' The 'oblong' is like the linear, the same size up and down, but it's much wider than the linear. The 'elliptical' is what the oblong would be if its ends were prettily tapered off. The apple tree has a leaf whose ellipse is so wide that it is called 'oval.' Can you guess what 'ovate' is?"

"'Egg-shaped'?" inquired Tom.

"That's it; larger at one end than the other, while a leaf that is almost round, is called 'rotund.'"

"Named after Della," observed Della's brother in a subdued voice that nevertheless caught his sister's ear and caused an oak twig to fly in his direction.

"There's a lance-shaped leaf that is sharp at the base instead of the point; that's named 'ob-lanceolate'; and there's one called 'spatulate' that looks like the spatula that druggists mix things with."

Linear Lance-shaped Oblong Elliptical Ovate

"That ought to be rounded at the point and narrow at the base," said the doctor's son.

"It is. The lower leaves of the common field daisy are examples. How do you think the botanists have named the shape that is like an egg upside down?"

"'Ob-ovate', if it's like the other ob," guessed Dorothy.

"The leaflets that make up the horse-chestnut leaf are 'wedge-shaped' at the base," Helen reminded them.

"Then there are some leaves that have nothing remarkable about their tips but have bases that draw your attention. One is 'heart-shaped'—like the linden leaf or the morning-glory. Another is 'kidney-shaped'. That one is wider than it is long."

Shield-shaped Oblancolate Spatulate Rotund Crenate Edge

"The hepatica is kidney-shaped," remarked James.

"The 'ear-shaped' base isn't very common in this part of the world, but there's a magnolia of that form. The 'arrow-shaped' base you can find in the arrow-weed in the brook. The shape like the old-time weapon, the 'halberd' is seen in the common sorrel."

Heart-shaped Kidney-shaped

"That nice, acid-tasting leaf?"

"Yes, that's the one. What does the nasturtium leaf remind you of?"

"Dicky always says that when the Jack-in-the-Pulpit stops preaching he jumps on the back of a frog and takes a nasturtium leaf for a shield and hops forth to look for adventures," said Roger, to whom Dicky confided many of his ideas when they were working together in the garden.

Arrow-shaped Ear-shaped Halberd-shaped

"Dicky is just right," laughed Helen. "That is a 'shield-shaped' leaf."

"Do the tips of the leaves have names?"

"Yes. They are all descriptive—'pointed,' 'acute,' 'obtuse,' 'truncate,' 'notched,' and so on," answered Helen. "Did you notice a minute ago that I spoke of the 'leaflet' of a horse-chestnut leaf? What's the difference between a 'leaflet' and a 'leaf'?"

"To judge by what you said, a leaflet must be a part of a leaf. One of the five fingers of the horse-chestnut leaf is a leaflet," Della reasoned out in answer.

Obtuse Truncated Notched

"Can you think of any other leaves that have leaflets?"

"A locust?"

"A rose?"

Pinnate Pinnate, tendrils Locust Leaf Sweet Pea Leaf

"A sweetpea?"

The latter answer-question came from Roger and produced a laugh.

"All those are right. The leaves that are made up of leaflets are called 'compound' leaves, and the ones that aren't compound are 'simple.'"

"Most leaves are simple," decided Ethel Brown.

"There are more simple than compound," agreed Helen. "As you recall them do you see any resemblance between the shape of the horse-chestnut leaf and the shape of the rose leaf and anything else we've been talking about this afternoon?"

"Helen is just naturally headed for the teaching profession!" exclaimed James in an undertone.

Helen flushed.

"I do seem to be asking about a million questions, don't I?" she responded good naturedly.

"The rose leaf is feather-shaped and the horse-chestnut is palm-shaped," Ethel Blue thought aloud, frowning delicately as she spoke. "They're like those different kinds of veining."

"That's it exactly," commended her cousin. "Those leaves are 'pinnately compound' and 'palmately compound' according as their leaflets are arranged like a feather or like the palm of your hand. When you begin to notice the edges of leaves you see that there is about every degree of cutting between the margin that is quite smooth and the margin that is so deeply cut that it is almost a compound leaf. It is never a real compound leaf, though, unless the leaflets are truly separate and all belong on one common stalk."

"My lily of the valley leaf has a perfectly smooth edge," said Ethel Blue.

"That is called 'entire.' This elm leaf of mine has a 'serrate' edge with the teeth pointing forward like the teeth of a saw. When they point outward like the spines of a holly leaf they are 'dentate-'toothed. The border of a nasturtium leaf is 'crenate' or scalloped. Most honeysuckles have a 'wavy' margin. When there are sharp, deep notches such as there are on the upper leaves of the field daisy, the edge is called 'cut.'"

"This oak leaf is 'cut,' then."

"When the cuts are as deep as those the leaf is 'cleft.' When they go about half way to the midrib, as in the hepatica, it is 'lobed' and when they almost reach the midrib as they do in the poppy it is 'parted.'"

Dentate Wavy

"Which makes me think our ways must part if James and I are to get home in time for dinner," said Margaret.

"There's our werwolf down in the field again," exclaimed Dorothy, peering through the bushes toward the meadow where a man was stooping and standing, examining what he took up from the ground.

"Let's go through the field and see what he's doing," exclaimed Roger. "He's been here so many times he must have some purpose."

But when they passed him he was merely looking at a flower through a small magnifying glass. He said "Good-afternoon" to them, and they saw as they looked back, that he kept on with his bending and rising and examination.

"He's like us, students of botany," laughed Ethel Blue. "We ought to have asked him to Helen's class this afternoon."

"I don't like his looks," Dorothy decided. "He makes me uncomfortable. I wish he wouldn't come here."

Roger turned back to take another look and shook his head thoughtfully.

"Me neither," he remarked concisely, and then added as if to take the thoughts of the girls off the subject, "Here's a wild strawberry plant for your indoor strawberry bed, Ethel Brown," and launched into the recitation of an anonymous poem he had recently found.