390 
SOME GENERAL PLANT PROBLEMS 
a dozen different types, and the first question to be settled 
is which shall be selected. This point is well shown in Figure 
357, which has two types of heads common in a field of oats. 
On the right is a branched head; on the left, the oat ker¬ 
nels are mostly on one side. Both these heads yield well, 
but the head that has the kernels on one side shows a greater 
tendency to lodge during a heavy wind or rainstorm, which 
makes this variety difficult to harvest. 
Before selection can be wisely undertaken, it is necessary 
to know the locality or environment in which the seed is to 
be sown and to learn which variety is best adapted to the 
locality. Some varieties are more resistant to drought than 
others, some are more susceptible to rust or more affected 
by smut, while others have stiffer straw, thicker hulls, or 
larger grain. 
Those who are making the experiments in plant breeding 
try to combine in one variety the best features of all, but it is 
difficult to produce just the results most desired. Many 
varieties of plants are improved regularly in nature by cross¬ 
pollination. In plant breeding man has taken advantage of 
this habit in plants and substituted pollen from a special 
variety when he sought to grow a plant with special features. 
But oats are regularly self-pollinated and when cross-pollina¬ 
tion is to be effected, the oat flower must be opened before it 
reaches the blooming stage and the three anthers must be 
removed. Then the flower is carefully closed and allowed to 
mature for two days before the pollen from the plant of the 
variety to be used is dusted on the pistil. 
The oat illustrates one of the difficulties which the plant 
breeder encounters. Each variety of plant has to be studied 
in just such a detailed fashion before any permanent improve¬ 
ment can be secured by plant breeding, which has become 
one of the most difficult and technical phases of plant study. 
322. Conservation. — Conservation is a term which was fre¬ 
quently heard during the war, in connection with sugar, coal, 
