1. Opposite leaves.—Examine a deadnettle plant (Fig. 92). Do the leaves come off the stem haphazard? How many come off at each level? Are both leaves on the same side of the stem, or opposite each other? Are the two leaves at the next level above just over these, or do the directions cross? Do the leaves get as much light or more than they would if each pair were just over the pair next below? How many other plants do you know which have leaves arranged in this manner? Examine leafy twigs of sycamore, horse chestnut (Fig. 40), and ash. Are the stalks of the lower leaves of these twigs of the same length as those of the upper ones? Is it any advantage for the lower leaves to have longer leaf stalks? 2. Box leaves.—What is the arrangement in the box? Examine particularly the young leaves near the end of the twig. Are the lower ones twisted? Can you suggest a reason for this twisting? Can you find any twigs in which no twisting has taken place? Are these untwisted twigs so placed that they are equally exposed to the light on all sides? 3. Alternate leaves.—Examine the arrangement of the leaves on a wallflower stem. They come off alternately, each springing from a rib on the stem. How many ribs are there? Look at the bottom of the stem, where the leaves have fallen off, and notice that each has left a scar. Mark one of the scars with your pencil and then count how many scars you pass before coming to another on the same rib. How many times do you wind round the stem in doing this? You pass five leaves and wind spirally round the stem twice. This is always the case in the wallflower. Examine leafy twigs of oak and pear trees. Here, too, the leaves are alternate, and every sixth leaf is above the first, and a line [Pg 45] joining all the leaf-bases or scars between the first and sixth leaves would wind spirally round the stem twice. What is the arrangement in the elm and lime? 4. Leaves which form a rosette.—Examine plants of primrose (Fig. 81) and daisy. The leaves in these cases spring from close to the ground and form a rosette. Notice that the bottom of the leaf blade is much narrower than the upper part. Is any saving of material obtained by this arrangement? 5. The position of branches and buds.—Look in the upper angle between a leaf and the stem in all your specimens. This angle is called the axil of the leaf. Can you see a bud in the axil of the leaf? Can you find that a bud or a side branch ever arises in any other position? (The former positions of fallen leaves are marked by scars.) To the beginner in nature-study leaves seem in the majority of cases to be arranged on the stem of a plant in a haphazard and confusing manner, and it is only after very careful observation that a definite order and regularity is seen to be always maintained.