About corolla-making,—if you are determined to know that, you will have to take yourself off to that far-away time when there were no flowers. Then, in course of time, while changing about and trying to get fitted to their surroundings, the plants, as you know, rolled some of their leaves into pistils and stamens. But still they had no petals. [Illustration: [Corolla]] The pistils and stamens were flowers, however,—as much flowers as they would ever be, no matter how much corolla they might develop. A corolla does not make a flower; by this time you know the important part of a flower is the pistil and stamens, and so, even to-day, some flowers, as the elms and some maples, have no petals at all. When such maples are in bloom, you will see gay fringes decorating the trees. This fringe is made of the long pedicels with the stamens at the end. The stamens swing in the breeze, and the pollen is blown to the stigmas which are often in flowers on different trees. Now, as plants grew and adapted themselves to their surroundings, they produced more seeds than could by any chance find room in the earth to grow. So every little seed that fell had to fight its way with a host of other seeds and plants. A defective seed or a weak one would stand no chance at all. The others would crowd it out. We know how that is in a garden. The delicate flowers have to be helped or the strong weeds would kill them. We pull up the weeds and let the flowers have the whole garden to themselves. But in the woods and fields each plant has to take care of itself and struggle up as best it can. This fight of the plants for a place to grow in is called the struggle for existence. Now, whatever would help a plant in the struggle for existence would, of course, be of great benefit to that plant. As we know, cross-fertilization is a very great help; it makes stronger and better seeds, and the plants whose seeds were regularly cross-fertilized would be the ones to survive. Where pistils and stamens are forming, there is a great deal of nourishment brought to that part of the plant, and substances are being changed there. Very often sweet juices are present. Long ago when insects, in flying about, smelled these sweets they doubtless would go and eat them, and they would also eat the pollen. As they went from flower to flower looking for food, they would carry pollen sticking to their legs or bodies, and so would sometimes fertilize the flowers. The seeds from such flowers would be strong and would have the best chance to survive. The plants that grew from these seeds would also inherit the tendency to secrete sweet juices near the flower. In probing for sweets, the insect would irritate the parts it touched, and this would cause an extra flow of sap there and very likely the manufacture of more sweet juice; so the nectary came to be developed.