IMPROVEMEXT BY SELECTION 43 



must be taken to prevent the introduction of pollen from 

 inferior plants. Thus an ear of corn may appear to be ex- 

 cellent, but some of the kernels may have been fertilize^ 

 by pollen from inferior stalks and the plants they produce 

 will be inferior. A large part of this ''bad l^lood" may be 

 eliminated by going through the field when the plants are 

 in tassel but before the pollen is shed and pulling out the tas- 

 sels of the weak, stalks and others that do not show promise 

 of producing good ears. The improvement of plants is 

 very interesting and should receive the attention of many 

 more persons than novr devote their energies to it. 



LABORATORY AND FIELD EXERCISES 



1 . Soak several beans or peas in tepid water for 24 hours. Then 

 examine them, noting how they have swelled and how easily the outer 

 skin may be removed. Separate the halves and examine the embryo 

 which remains attached to one of them. At the same time put a fe\\' 

 beans in ice water and keep the water below 40 degrees, if possible, 

 }jut avoid actual freezing. Note how httle the seeds have swelled 

 in comparison with the others. Also soak a few beans for the same 

 length of time in tepid water containing a spoonful of common salt. 

 Note that they have not swelled as have those in warm water. Seeds 

 have the power of keeping out undesirable solutions and will not germi- 

 nate in soils containing any considerable quantity of salts. 



2. Plant several beans in a small box of good soil; plant kc^rnels 

 of corn in a similar box. Keep the soil moist, but not wet. hi a few 

 days the plants will appear. Note how the young shoot of the bean 

 has pushed the halves of the seed apart and forced them to the surface, 

 wliile the kernel of corn r( n ained below. Dig up one plant of each 

 carefully and note the difference in the root system; also how the young 

 corn plant is still attached lo the kernel. A few days later note that 

 the thick halves of the bean have gi-adually disappeared; also that the 

 corn kernel has decreased till little more than a shell is left. The plant 

 is drawing on its supply of food stored in the seed. Soon the green 

 leaves will begin to manufacture food from the air, while the roots will 

 draw on the supply in the soil. 



3. Plant beans in another box or pot. As soon as they appear 

 above ground, cut off parts of the thick "seed leaves" with a knife, 

 being careful not to injure the young plant. Leave one or two plants 



