PROBLEM 22 51 



Heat the slide very slightly. What is the result? Cool the 

 slide and note the effect on cell movement. 



Conclusion. — 1. In what part of plants may protoplasm be 

 found ? 



2. Write a paragraph, describing the appearance, movement, 

 and composition of protoplasm in Elodea. What are its reactions 

 (look up this word in the dictionary) to heat and cold ? 



Probletn 21 : To study structure and growth of pollen. 



Materials. — Pollen of snapdragon, sweet pea, nasturtium, or 

 tulip; sugar solution (3 per cent, 10 per cent, and 15 per cent), 

 bell jar, sponge, a compound microscope, hand lens. 



Method. — Dust some pollen of snapdragon on a glass slide. 

 Examine it with a hand lens. Make a 10 per cent solution of cane 

 sugar and dust some ripe pollen in a drop of the solution placed 

 on a glass slide. Place this slide under a small bell jar with a 

 moist sponge and examine after 24 hours with the low power of 

 the compound microscope. Try sweet pea or nasturtium pollen 

 in 'a 15 per cent sugar solution, or tulip with a 3 per cent sugar 

 solution. 



Observations. — Look for a tubelike structure, the ■pollen tube, 

 growing out of the pollen grains. Describe and sketch one. 



Conclusion. — 1 . What made the pollen tube grow ? 



2. Under what other condition have you heard of the growth of 

 pollen ? 



Problem 22 : To study the reason for the growth of pollen 

 grains in flowers. 



Method and Observations. — Study the following diagram, the 

 figures, pages 53 and 54, in your Civic Biology, and charts 

 for further explanation. Within the pollen tube is a cell known 

 as the sperm cell. Note that the cell in the end of the pollen 

 tube is about to unite with the egg. Observe the pathway taken 

 by the pollen tube. How does the sperm cell from the pollen 

 grain get into the ovary? Study the longitudinal section of the 

 ovary. Note a number of ovoid bodies (ovules) in the ovary. 

 How could a pollen tube reach an ovule ? 



