Abnormal Growth 



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deal of attention among morphologists. Much of the literature is reviewed 

 in the papers of Schoute (1936), Bausor (1937), and O. E. White (1948). 

 The term fasciation, like others in the field of abnormal growth, has 

 been applied to a rather wide variety of phenomena which probably have 

 different origins even though the final result in all of them is a flattened 

 structure. Frank (1880) distinguished between fasciations that arise by 

 a gradual expansion of the growing point in one plane and others that 

 come from lateral fusion or connation between two or more separate 



Fig. 11-4. "Witches'-broom" on a fern leaf. (After Giesenhagen.) 



structures, in natural self-grafting. Schoute believes that the term fasci- 

 ation should be limited to Frank's first category, and this is now the com- 

 monest practice. The difference between the two concepts can be deter- 

 mined only by developmental studies. Johansen (1930) has shown that 

 the genesis of fasciation may be recognized even in early embryogeny. 



Fasciation is most conspicuous in the main-shoot axis but occurs also 

 in roots (Schenck, 1916) and may be found in almost all parts of the 

 plant. It may vary from one part to another. Many abnormalities resem- 

 bling fasciation are to be seen in leaves, such as "double" leaves and 

 others. 



