TAXONOMIC SUMMARY ILLUSTRATIONS 17 



one region being included in each) is : Boreales : Total 66 ; United States 

 28; Mexico 48; Central America 2; West Indies 0; South America 0. 

 Aequatoriales : Total 211 ; United States ; Mexico 29 ; Central America 

 20 ; West Indies 38 ; South America 134. 



Of the Boreales 41, or two-thirds, and of the Aequatoriales 87, or two- 

 fifths, are now characterized as new. A very large percentage of the 

 forms that have been accorded specific rank by earlier writers are still 

 kept up even though they had passed into synonymy. Later studies, 

 especially in the field, in the light of the conclusions now reached, may 

 be looked to with confidence not only to bring to recognition many spe- 

 cies not yet collected, but to make possible the trustworthy subordina- 

 tion or merging of some of the forms that are now held for species. As 

 my study has proceeded, I have had the satisfaction of finding my own 

 opinion in accord with the view of a number of the most experienced 

 systematists, that in a monographic assemblage such as is here offered 

 no lasting harm can come from the most radical segregation of forms 

 possible on morphologic and geographic considerations, while on the other 

 hand a blending of widely dissociated forms or of such as differ greatly 

 in their extremes though without as yet definable breaks in the series, 

 e.g. P. piperoides, leaves the work to be taken up once more from the 

 very foundation, and with reference to all of the original materials that 

 may have survived. 



ILLUSTRATIONS 



To any one who has ever wished to compare an American mistletoe 

 with an authentic illustration, it has become evident at once that such 

 illustrations scarcely exist apart from the superb plates on which Eichler 

 figured many of the Brazilian species. It has been my aim to picture 

 the more essential features of every species without alteration of size, by 

 aid of the camera, and if possible from type specimens not only of the 

 species as accepted but of forms which have been given names that have 

 passed into synonymy. That every species has been figured, and that 

 scarcely a half-dozen types, even of synonyms, are unpictured, may be 

 my excuse for adding that words are lacking to express adequately my 

 gratitude to the many botanists of Europe and North America who have 

 opened their collections to me without restrictions, and in some cases 

 have allowed type material to follow me across the Atlantic or have re- 

 placed photographs which were unsatisfactory in the first instance. That 

 the manuscript now completed for publication pictures for the first time 

 237, or nine-tenths, of the recognized forms, shows more clearly my debt 

 to these friends than can be stated in any other words. 



The University of Illinois, 

 January, 1, 1916. 



