3. Plot the curves and determine the Deviations in the 

 number of ribs in the leaves of two beech trees, after Walter : 



Bud or Clonal Variations 



Sometimes buds arise on plants that produce branches 

 dififering markedly from the other branches. Such are called 

 bud variations, and are often found on roses, coleus, carna- 

 tions, nephrolepis, and chrysanthemums. ' Some bud varia- 

 tions are undoubtedly mere fluctuations, but many are dis- 

 tinct mutations. Both types can be used in breeding— e.g., 

 violets, potato, and rose. Webber has shown that the var- 

 ious types of oranges, such as nobilis, aurantium, decumana, 

 limonum, myrtijolia, and trijoliata have arisen as bud muta- 

 tions from a single original form. A study of these types 

 show Progressive, Retrogressive, and Regressive forms. 

 Not much is really known about the causes producing bud 

 variations, but probably their origin is due to the same 

 causes that produce the mutations occurring in sexual re- 

 production. 



The Washington Navel or seedless orange arose as a bud 

 sport found at Bahia, Brazil, in 1826, and brought to 

 Washington about 45 years ago. 



Causes of Variations 



Darwin said (Origin of Species): "Our ignorance of 

 the laws of variation is profound. Not in one case out of a 

 hundred can we pretend to assign any reason why this or 

 that part has varied." This statement still holds true to- 

 day. Some biologists maintain that variabilitv is a prim- 

 ary property of organisms while others regard variations as 

 the result of causes either extrinsic (Lamarckian) or in- 

 tnnsic to the organism. For convenience, the causes of 

 variation may be classified as (1) Internal, and (2) External. 



(1)— Read stout on Bud Selection in Coleus (Publ. 218 Carnegie Inst) 

 Inst.) and Coit's Citrus Fruits. v..xi.iceic ±nai..) 



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