[Chap. XXXVI ORIGIN OF PLANTS USED BY MAN 435 



mass selection in the attempted improvement of many cultivated plants. 

 This method may be illustrated by one example. David Fife of Canada 

 secured a small sample of hard spring wheat from a friend in Scotland. 

 When he planted the wheat in a small plot in Canada in the spring of 

 the year, he discovered that this new wheat was a winter wheat and 

 should have been planted in autumn. A single plant in the plot, however, 

 developed as spring wheat. Seeds from this single plant were saved and 

 planted. This one plant is the ancestor of all the Red Fife wheat now 

 cultivated in Canada and the United States. 



Red Fife, in turn, when crossed with Hard Red Calcutta wheat from 

 Turkey, became one of the parents of the famous Marquis wheat, which 

 for 20 years was regarded as the king of hard red spring wheats. In time 

 it became surpassed by some of its more desirable progeny. 



In contrast to corn, crops of close-pollinated plants, such as wheat, 

 oats, and barley, are composed of inbred lines. The story of the search 

 for new varieties of plants, as summarized in the 1936 and 1937 Year 

 Books of Agriculture, portravs modern methods of securing new varieties 

 of domesticated plants, and also the magnitude of this enterprise. 



The work of botanists during the second half of the 19th century is 

 remarkable for the number of important facts discovered about plants. 

 In 1866 Gregor Johann Mendel, an abbot of Briuin, Austria, after eight 

 years of experiments formulated certain general principles about hybrid 

 variations in the garden pea that were later found to have general appli- 

 cation to both plants and animals. In 1900 the principles fonnulated by 

 Mendel and also his publication, which had been forgotten, were re- 

 discovered independently by de Vries of Holland, Correns of Germany, 

 and Tschennak of Austria.'* These principles have been thoroughly- 

 tested bv means of numerous experiments and they are now widely used 

 as a scientific basis for further investigation and interpretation of 

 heredity. 



About the same time, de Vries began to emphasize the importance 

 of another type of heritable variation in plants that is not dependent upon 

 hybridization; it is known today as a mutation. Mutations had been 

 noted earlier and referred to by various names, but their importance had 

 not been recognized. The change of yellow to red sweet potatoes illus- 

 trated in Plate 4 is one example of a mutation. Another example on the 



^ After eiglit vears of experiments with the progeny oljtained by cross- and self- 

 fertilization in the garden pea, Mendel published his data and conclusions in the Proceed- 

 ings of the Briinn Natural History Society in 1866. 



