The Significance of the Atavists. 557 
decussate individuals. On the lateral branches of these 
whorled stems, on the other hand, 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 ; 
and 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 A B), and in all degrees of split- 
ting from leaves with two tips to leaves split down to 
the base. 1 Sometimes they even produce one or two 
ternary whorls in the upper parts of the plant. The 
range of variation in these splittings has been dealt with 
by DELPiNO, 2 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 there usually arises, ac- 
cording to my observations, a single shoot ; but sometimes 
two of them, or a single broad flattened one with two 
1 Bcr. d. d. hot. Gcs., Vol. VII, 1889, p. 296. 
2 F. DELPINO, Teoria gcneralc dclla Fillotassi, Atti della R. Uni- 
versita di Geneva, IV, Parte II, 1883. 
