FLORA OF VERMONT 93 



III. THE PRINCIPAL GENERA OF ANGIOSPERMS 

 Including all having ten or more species 

 Monocotyledons 



IV. THE NATIVE FLORA 



It is often difficult to determine whether a plant is native or intro- 

 duced. In the above summaries those plants are classified as " native," 

 which are considered to be natives of northeastern America and which are, 

 therefore, printed in full-face type in the catalogue, following the usage of 

 the Gray Manual. This is not strictly correct, since a number of such 

 plants have recently been added to the original flora of Vermont from the 

 more immediately adjacent parts of this continent. Some of these like 

 Rudbeckia hirta and Hordeumjubatum are clearly recognizable as introduced, 

 while others like Cenchrus tribuloides and Chenopodium capitatum are appar- 

 ently natives in some localities, although plainly not so in others. 



The problem is further complicated by the fact that natural agen- 

 cies other than man are operative in plant distribution. For ex- 

 ample birds not only disseminate seeds locally, but at the migrating season 

 they may carry them long distances. Probably some of our newly recog- 

 nized forms of Crataegus have been brought from the South by migrating 

 crows or other birds within recent years. Disregarding these more natural 

 agencies we have attempted to select from among the species considered to 

 be natives of this continent and, therefore, printed in full-face type in this 

 catalogue, such as have in our judgment been introduced in Vermont by 

 the direct or indirect agency of the white man. This list is doubtless 

 incomplete and imperfect. In our judgment, however, the following plants, 

 except where marked questionable, have been introduced in Vermont. 

 Those followed by a question mark occur usually, if not always, as intro- 

 duced plants, but it is possible that they may also occur occasionally as 



