IDS 



THE AMERICAN NATURALIST [Vol. XLII 



known to be phenogamous by the character of their flores- 

 cence and fruitage, but for this occasion they are classified 

 by their parasitic differences only. They are divided into 

 no less than seven distinct groups, or kinds, which differ 

 in character from root pilfering by means of a few haus- 

 toria to dominant rapacity, extreme deformation of so- 

 matic and embryonal structure and aberrant methods of 

 germination. ( 2 ) The method of parasitism of each group 

 is shared equally by every member of it, whatever may be 

 the systematic affinities of the respective members, and 

 the method of each group is entirely unlike that of every 

 other group. (3) All the parasitic habits and structures 

 are severally and completely heritable, and always con- 

 nate with systematic features of the species in which they 

 occur, but they are never systematically correlated with 

 them. (4) None of the seven forms of parasitism shows 

 any tendency to return to normal conditions, to become 

 more complex, or to change from one form to another. 

 (5) The normal florescence and fruitage of the parasites 

 is assumed to indicate that they were originally derived 

 from normal phenogams; but no trace of intermediate 

 stages between even the most extreme cases of parasitism 

 and normal plants has been discovered. The geograph- 

 ical distribution of all the known kinds of phenogamous 

 parasitism, except that of group III, is almost world-wide. 

 In consideration of these, and many kindred, facts it is 

 assumed that the phenogamous parasites originated as 

 such by sudden and aggregate mutation from normal 

 phenogams, similar to, but not identical with, the phylo- 

 genetic aggregate mutation that has been observed in 

 Lycopersicum and Gossypium. 



