The Siynificojice of the Atavists. 557 



decussate individuals. On the lateral branches of these 

 whorled stems, on the other liand, these splittings, as 

 well as local torsions and other anomalies are by no means 

 rare. 



The relation of the ternary whorl to the spiral ar- 

 rangement demands closer investigation. Perhaps the 

 former is to be regarded as a lower stage of the anomaly ; 

 arid this view is supported by the fact that highly twisted 

 individuals which have one or more straight internodes 

 above the torsion, usually exhibit ternary whorls between 

 them. 



The decussate individuals often produce leaves with 

 split midribs (Fig. 131 AB), and in all degrees of split- 

 ting from leaves with two tips to leaves split down to 

 the base.-^ Sometimes they even produce one or two 

 ternary wdiorls in the upper parts of the plant. The 

 range of variation in these splittings has been dealt with 

 by Delpino^^ and material for a complete demonstration 

 of these forms may be furnished by every generation of 

 my race. 



In the third generation I left three atavists on the bed 

 until shortly before they flowered. They all bore some 

 split leaves in the upper part of their stem; in the ninth 

 generation I observed the same anomaly on the main 

 stems of 172 of the 200 decussate atavists, that is to say, 

 in about 80% of the whole group. Several of the re- 

 mainder exhibited the anomaly on the lateral branches. 



From the axil of a split leaf tliere usually arises, ac- 

 cording to my observations, a single sh(^ot ; but sometimes 

 two of them, or a single broad flattened one witli two 



' Bcr. d. d. hot. Grs., Vol. VTI. iSSg. p. 296. 



" F. Delptno. Tcon'a (^enrralr dcUa Fillolassi. Atti della R. Uni- 

 versita di Geneva, IV, Parte IT, 1883. 



