26 A FIELD GUIDE IN NATURE-STUDY 



* 



are the four yellow petals making up the corolla. These inclose and protect 

 the essential parts of the blossom, stamens, and pistil. Four of the stamens 

 are of equal length, two others longer. Note that each stamen consists of 

 (i) a basal stalk, the filament, which bears (2) an elongated case, the anther, 

 in which the pollen is held. You have probably noticed this yellow dusty 

 pollen in the Easter lily or possibly in the buttercup and as a child have put 

 your nose into some flower for the purpose of getting it colored with the 

 yellow pollen. At the center of the flower is the pistil, made up of (i) a 

 swollen base, the ovary, (2) a stalk-like style, with (3) a sticky knob at its 

 end, the stigma. Parts similar to these will be found in any of the other 

 flowers. 



Origin of fruit. Examine a mustard plant old enough to show the seed 

 pods. Where are the largest seed pods ? Following up the younger and 

 younger ones you see that the seed pod arises from what ? With a sharp 

 knife make a section of such a large ovary as is to be found in the nasturtium 

 blossom or mandrake. There will be seen a number of tiny objects looking 

 like diminutive seeds. These are really the ovules. In them are the eggs, 

 tiny things that can be seen only under the microscope. Read up the 

 process by which the egg is fertilized by means of the pollen and what hap- 

 pens in consequence and write a statement of it that would be intelligible 

 to a sixth-grade child. 



All living things from eggs. Open mature pea pods. Do you find, in 

 some of them, in addition to the well-formed peas, some tiny objects grow- 

 ing where you would expect a pea to be ? These are the ovules whose eggs 

 were inadequately fertilized. Unless the egg in the ovule is fertilized it 

 does not grow into the new little plant. It is well-nigh universally true 

 that except among the very simplest animals and plants every living thing 

 comes from an egg and that this must be fertilized before the developmental 

 process will begin. 



Anemophilous and entomophilous flowers. Fertilization is so important 

 that plants have many devices to make it certain. Some flowers are self- 

 pollinated; that is, the pollen of the stamens is dusted onto the stigma of 

 the same flower. Such flowers do not need to open at all. But as a rule 

 the pollen is carried to another flower, for it has been proven that more 

 seeds and seeds with greater vitality are produced by cross-pollination 

 than by self-pollination. In general the plant either depends for cross- 

 pollination (i) on an abundance of pollen so that the wind will carry it 

 from flower to flower or (2) on insect visitors. The ragweed is an example 

 of a wind-pollinated plant. Shake a large plant of this kind growing in 

 the field and see it "smoke" as the pollen falls in clouds. Such wind- 

 fertilized plants usually have inconspicuous blossoms. 



