PLANTS. 75 



field to another, will produce scattering kernels in the 

 latter field of the variety contained in the former. 



QUESTIONS, 



What are plants ? What are the two essential parts of a seed ? 

 What is the embryo ? How long will seeds preserve their vitality ? 

 Why should new seeds be used for planting ? What is the effect 

 of planting unripe seeds? What is the effect of selecting the best 

 specimens of seeds for planting ? 



What are the three conditions necessary for the growth of seeds ? 

 How much moisture is most favorable ? What is the effect of 

 planting seeds in soil either too warm or too cold ? What is the 

 effect of planting seeds too early in the spring ? Why will seeds 

 fail to grow where there is no air ? Under what circumstances is 

 it best to plant seeds deeply ? When is it better to cover them but 

 lightly ? What causes weeds to spring up after ground has been 

 plowed ? Why have these weeds failed to grow before ? 



What are the three processes involved in germination ? Why must 

 the seed be filled with moisture ? Why is grain allowed to sprout 

 in making malt ? Why does sprouting produce heat ? 



What are the radicle and the plumule ? Why do they start from the 

 seed in opposite directions ? Which is more essential to the plant, 

 the atmosphere or the soil ? In what points do plants, in their 

 growth, resemble animals ? 



Name the elementary substances that are essential to the growth of 

 plants. What food do plants obtain largely from the atmosphere ? 

 Explain the process by which it is obtained. What has the sun- 

 light to do with it ? Why do plants become pale in dark weather ? 

 How do plants purify the air ? Do they remove oxygen from the 

 air ? Do they purify the air in the night ? Are they beneficial to 

 the air in a dwelling-house ? How are drooping plants revived by 

 watering? Do plants obtain nitrogen from the air? 



What are the purposes of roots ? Name some plants which have tap- 

 roots ? By what method do roots grow ? How many roots have 

 plants? How deep do they sometimes extend? 



Name all the elements of food that plants obtain from the atmos- 

 phere. Name those that they obtain from the soil. How do they 



