“But I am coming to an example that will be more familiar to us. The pumpkin is monœcious: flowers with stamens and flowers with pistils inhabit the same house, the same vine. Before they are full-blown they can easily be distinguished from each other. The flowers with pistils have under the corolla a large swelling which is the ovary, the future pumpkin. The blossoms with stamens have not this swelling. Well, from one pumpkin vine standing apart in the garden let us cut off all the buds with stamens before they open, and leave those with pistils. For greater surety we will wrap each one of these latter in a piece of gauze large enough to let the flower develop without hindrance. This operation must be carried out before the buds open, in order to make sure that the stigmas have not already received any pollen. Under these conditions, not being able to receive the vivifying dust, since the flowers with stamens are cut off, and since also the gauze wrappings keep out the insects that might bring the pollen they had pilfered from some neighboring pumpkin vine, the pistillate flowers will wither after languishing awhile, and their ovaries will dry up without growing into pumpkins. If, however, we wish any selected blossoms to fructify in spite of their gauze prison and the suppression of the staminate blossoms, we take a small camel’s hair brush and gather a little pollen which we put on the stigma. That is enough, the pumpkin will come. “The absolute necessity of pollen for the formation of fruit explains to us the harmful effect of violent winds and prolonged rains in blossoming time. Swept away by blasts of wind, or washed away by rains, or simply spoiled by long-continued moisture, the dust of the stamens no longer acts on the ovaries, and the flowers fall without fructifying. This ruin of the harvest from lack of pollen is known as blight.” CHAPTER XXXII THE GRAIN OF WHEAT “Now turn your attention to this picture of an ivy seed cut through lengthwise. Where is the germ or little plant in its egg? It is that little white thing, rather long and narrow, embedded in the substance of the seed at one end. A fine line marks the division of the two cotyledons, which are now pressed close together. Next to them comes the tigella, or little stalk, ending in the radicle, or rootlet. Notice, my friends, how small these cotyledons are, how different from the enormous nursing-leaves of the almond, acorn, broad bean, kidney bean, and pea. These poor little plant-udders must soon get dried up, and if there were no other resources available at the time of germination the ivy would speedily starve to death.