CHAPTER XLV 



PLANT BREEDING 



Questions. 1. How can plants be made to vary? 2. Will plants that 

 have better growing conditions produce better offspring ? 3. Can plants 

 of two different species produce offspring if the pollen is crossed? 

 4. Why do plants resemble their parents ? 5. Why do plants differ from 

 their parents ? 6. How are new breeds of plants produced ? 



366. Inducing variations. Improvements in domestic plants 

 (as well as in animals) have come from preserving and multiply- 

 ing those individuals that shov^ed some superiority over their 

 fellows. For a long time, therefore, people have tried to find 

 ways of bringing about variations in plants. It was expected 

 that, while some of the variations might be useless or even 

 undesirable, some at least would tend to be useful. How can 

 variations be brought about? Certainly we know that plants 

 supplied with favorable conditions from the time the seed 

 germinates will thrive better than those not so favored; well- 

 conditioned corn will produce larger seeds, well-conditioned 

 potato plants will produce larger tubers, and so on. Taking 

 good care of organisms is thus the first step in their cultivation. 

 But sometimes a change in one condition or factor brings about 

 a marked difference in results. Raising wheat in a colder region 

 might shorten the time between planting and ripening. ]\Iore 

 iron in the soil might change the color of the blossoms. Shading 

 the plants might result in larger, thinner leaves. By giving their 

 plants the most favorable conditions for development, and by 

 changing one or another condition, cultivators have attempted 

 to increase the chances of finding desirable variations. 



Another source of variation was found in hybridizing. This is 

 the procedure of crossing two strains of organisms. For example, 

 the pollen from one variety of orange is placed on the stigma 



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