110 A/ai'isiii. 



])icions indicated above. T mean that they occur so rarely 

 and in so few indixidnals tliat the possibih'ty of a previous 

 cross, by means of insects, with the pohen of alhed forms, 

 even if growing a long way off, can never be quite ex- 

 cluded. It is only in cases in which, as in that of Ocno- 

 ihcra sciutilhvis ( \^ol. I, pp. 245 and 2)77), a species pro- 

 duces a large number of atavistic individuals every year, 

 that the phenomenon easily lends itself to experimental 

 study. 



On account of the circumstances indicated, it is not 

 possible to say whether atavism in plants propagated by 

 seed is a common or a rare phenomenon. It is certainly 

 much rarer than the practical gardener usually imagines. 

 I have observed in my cultures a number of cases which 

 might have been called atavistic with more or less cer- 

 tainty, but only the cases of regularly inconstant races, 

 such as those of Plan fa go and Linaria, and the ])henom- 

 ena presented by striped flowers, to be described shortlv, 

 seem to me to be sufficiently well established to be ad- 

 duced as instances of atavism. 



Atavism by bud-variation, on the other liand. is a 

 well-known phenomenon. One of the best instances is 

 shown in Fig. 16. It represents a vertical branch of a 

 bush of Ccphalota.vus pcdunculata fastigiata (Podocarpus 

 Koraiana Hart). Below the middle of tlie figure can 

 be seen the place where a branch has been cut oft, and 

 from the side of its base some lateral branches have arisen 

 with flat spreading leaves (Fig. 16 A). ^ The variety 

 Fastigiata has erect branches only and their leaves are 

 inserted on all sides : but the branches at A have the 

 structure of the parent species, C. pcdunculata \ tlieir 



^ For a series of interestin,£? experiments relating to this subject 

 see Mutations ct fraumafisiiics by L. Blarixgtiem (Note of 1909). 



