POND, LAKE, AND STREAM 21 



kins were longer and were hanging down. There was no 

 honey in them and therefore no insects were attracted to 

 them ; but the least breeze shook the long tassels and car- 

 ried the pollen from the staminate to the pistillate flowers. 

 The poplars are fertilized by the wind. Can you think of 

 other plants that are wind-fertilized ? 



The largest poplar is the Cottonwood Poplar. In rich 

 and moist soil it grows very fast, and sometimes reaches a 

 height of one hundred and fifty feet. The seeds of the 

 poplars resemble those of the willows, and they are also 

 disseminated by the wind. Other common and well-known 

 poplars are the American Aspen and the Balsam Poplar, or 

 Balm of Gilead. 



Which poplars are planted for shade and ornament? 

 Do you know what their wood is used for ? Can you see 

 any reason why poplars and willows should be much more 

 common than butternut and walnut trees? 



15. The Frog. 



MATERIAL : In early spring, place some frog eggs in a fruit jar. 

 Change the water about every third day. Take the water out of a 

 brook or pond where frogs and tadpoles live. Do not take well or 

 cistern water. Feed the tadpoles with a few crumbs of wheat bread 

 or water crackers. Later on, put a few small water plants into the 

 jar ; change them when no longer fresh. When the legs begin to grow 

 on the tadpoles, place a few pieces of wood or a small ladder into the 

 jar. Several species of frogs in a fruit jar. The jumping, swimming, 

 and croaking of frogs must have been previously observed outdoors. 

 You ought to have some eggs and tadpoles at different stages of de- 

 velopment preserved in weak alcohol. 



In early spring we found clumps of frog eggs. Each 

 egg looked like a little ball of jelly, and had a dark spot in 

 the centre. The gelatinous covering at first protected the 

 real egg in the centre, but when the little tadpole began to 

 develop it fed on this jelly. What did it eat later on ? 



Is the rock iu the quarry stratified ? 



