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ELEMENTARY SCIENCE 



of the common ferns, but it does not look like a fern at all. 

 Its name is Selaginella (club-moss). This plant produces 

 two kinds of spores, a big kind and a little kind. The 

 big kind produces a structure that bears eggs only. The 

 little kind produces a structure that bears sperms only. 

 The sperms have to swim about to find the eggs. And 

 still there is nothing that looks like a 

 seed! 



But the seed appears with the very next 

 step. You probably know that flowers pro- 

 duce pollen. Pollen is a dust-like sub- 

 stance (commonly yellow), and you find it 

 at the ends of those structures inside the 

 flowers that are called stamens (see Fig. 95). 

 Surely you have heard that insects (es- 

 pecially bees) carry pollen from flower to 

 flower as they go about searching for food. 

 Now, a grain of pollen is a spore. But we 

 know that seed-plants produce two kinds 

 of spores. Where is the other kind ? 



If you dissect a flower you will nearly al- 

 ways find at the very center of it, and at 

 the bottom, the little structure that is go- 

 ing to become the fruit. If you cut open 

 this structure you will find inside of it the very small 

 structures that are going to become the seeds. These 

 baby seeds are called ovules and the structure that con- 

 tains them is called the ovary (see Fig. 96). It is inside 

 the ovules that the big spores are produced, and they 

 never escape. It is this that gives us seeds. The big spores 

 produce eggs. These eggs are hidden away inside the 

 ovules, and the ovules are hidden away inside the ovary. 



FIG. 96. Longi- 

 tudinal section of 

 an ovary, show- 

 ing ovule and pol- 

 len tubes. After 

 J. M. COULTER. 



