with advantage producing, among others, the seedless 

 apple, the large white blackberry, the spineless cactus, the 

 Shasta Daisy (a triple hybrid of American, English and 

 Japanese daisies) the rapid growing Royal walnut, (a hybrid 

 of Juglans calif ornica x /, nigra), and the dewberry-rasp- 

 berry, the plumcot (a hybrid of plum and apricot.) 



East is of the opinion that this phenomenon of increased 

 vigor of hybrids may account for the frequency of cross- 

 fertilized species and the rarity of self-fertilized species, 

 since it can be shown that there is no evil effect due to in- 

 breeding per se. 



Exercise. — Give cases of increased hybrid vigor, other 

 than those cited above. 



Uses of Hybrids: 



Summarizing we may say that hybrids are produced: 

 to obtain a combination of desirable characters not 

 present in other plants, e.g. many of Burbank's 

 productions, 

 to get rid of undesirable characters such as suscepti- 

 bility to disease, drought and cold, e. g. work of 

 Biffen with wheat and Webber with critus 

 fruits; and 

 to secure greater vigor and more rapid growth, e.g. 

 work of Burbank with walnut trees, and that 

 of East and Shull with corn. 



Chapter 15— THE EXPERIMENTAL METHOD OF 

 INVESTIGATING HEREDITY 



The second method of studying heredity is by direct 

 experimentation after the method of Mendel and his follow- 

 ers. (Seep. 46) , . ,, , ,. 

 ^ ^ ' (a) — Mendehsm 



The laws of Inheritance in hybridism were first deter- 

 mined by Abbe Gregor Mendel^ and published in 1865 in 

 the Proceedings of the Natural History Society of Brunn^ 



(1) — Mendel was born at Heinzendorf in Austrian-Silesia in 1822 and 

 was educated at the Gymnasia of Troppau and Olniutz. He 

 entered the Augustinian Monastery at Brunn where he became a 

 noted teacher. He studied mathematics, physics and natural 

 sciences for two years (1851-1853) at the University of Vienna, 

 and in 1868 became Abbot of the Monastery. He corresponded 

 with the Botanist Nageli who was the only great naturalist 

 acquainted with his experiments on peas. He died in 1884. 



(2) — The French botanist Naudin published in 1862 the results of 

 researches in plant hybridization which harmonized with those 

 of Mendel, but he failed to grasp the idea that the segregation 

 applies to "single" characteristics rather than to all the char- 

 acteristics of a species at once! No doubt Mendel was acquainted 

 with his researches as well as those of his predecessors, JCol- 

 reuter. Knight and Goss (See Lock). 



81 



