106 THE AMERICAN NATURALIST [Vol. XLII 



bear an outward resemblance to fungi, to which early 

 botanists referred them. The genera of this group are 

 still further distinguished by the comparatively small 

 number of species which represent them, the average 

 number to the genus being less than three. Yet all the 

 members of this remarkably diversified group are devel- 

 oped from a simple filiform embryo by a germination 

 similar to that of the broom-rapes, and all are rigidly con- 

 trolled by one invariable and heritable method of para- 

 sitism. It is almost superfluous to add that there are no 

 known intermediate forms between the parasitic species 

 of this group, or between them and normal phenogams. 



A leading purpose in the foregoing remarks is to ex- 

 press the belief and present evidence that all the various 

 methods, or forms, of phenogamous parasitism have 

 originated suddenly by abnormal mutation from normal 

 phenogams and that each form originated independently 

 of all the others. One can not doubt that, whatever may 

 be the determinate cause, all mutations of plants, whether 

 normal or abnormal, originated in changes of molecular 

 conditions within the germ cell. Usually, those molecular 

 changes are of phylogenetic character, but there is no 

 reason to doubt that the changes which gave origin to the 

 various parasitic attributes were also of like molecular 

 origin. That is, referring to the theory of intracellular 

 pangenesis of de Vries, each of those attributes, as well 

 as their associated abnormalities of structure, both so- 

 matic and embryonic, had its origin in abnormal pan- 

 genes. Admitting such a community of molecular origin, 

 there appears to be no more reason to doubt the origina- 

 tion of parasites by aggregate mutation than to doubt 

 normal aggregate mutation. 



One who accepts without qualification the theory of 

 the origin of species by natural selection is no more 

 likely to favor this idea of the sudden origination of 

 the great and diverse groups of parasites which have 

 been referred to in preceding paragraphs than he would 

 be to accept the theory of special creation of species, 



