18 



has come into intimate contact with the group flavescens, especi- 

 ally in the field, will have felt the need of a segregation of forms 

 on some consistent basis and no doubt this will have been the 

 experience of botanists in other geographic regions occupied by 

 Phoradendron. 



Now if we had a greater fund of knowledge about American 

 Loranthaceae based on investigations in the morphology, 

 physiology and ecology of the group, particularly if we had data 

 based on continued studies and cultural experiments in the field, 

 no doubt structural and growth-habit characters would suffice 

 alone for a basis of segregation of forms. Professor Trelease 

 has pointed out the shortcomings of dried herbarium specimens 

 in furnishing such a reliable basis. In the absence of the fuller 

 measure of such knowledge as that just specified, it is possible to 

 bring to the support of this knowledge the facts of geographical 

 distribution. This the author has done and one is impressed by 

 the fact that the taxonomic scheme of Phoradendron offered by 

 Professor Trelease is virtually a projection of the genus upon the 

 geographic regions occupied by it. To be sure the number of 

 geographic regions indicated (twenty-two) is only two fifths of 

 the number of species, groups or sections defined (fifty-five) so 

 that of course structural differences have been given due weight, 

 nor must one infer that the species of any group are wholly con- 

 fined to a single geographic region. But the mere mention of 

 Sonoran region, Andean region, Caribbean region, etc., carries 

 the presumption of forms of Phoradendron characteristic of or 

 even peculiar to each. 



This reviewer is led to remark upon the significant influence 

 phytogeographic studies are having and are destined still more 

 to exert upon taxonomic revisions of groups. The latter studies 

 have of course aided in the definition of geographical provinces, 

 regions, etc., but with even our present knowledge of the values 

 of the geographic factors one may have in advance, in taking up a 

 group such as the mistletoes, a certain degree of expectation as 

 to what the segregation will be. And this invites also the 

 further comment that the character of the monograph is being 

 changed by the advancing point of view given of course by the 



