234 Scientific Intelligence. 



migrate to a distance, while others have been modified to adapt 

 themselves to the gradual changes of the environment. Many 

 vegetable groups, which are but slightly represented in the higher 

 region of the Andes, such, for instance, as the Melastotnacece, 

 probably had their origin in the mountains of ancient Brazil." 



We are now only beginning to reach some conception of the 

 role which the Andes and their prolongation through Mexico have 

 taken in determining the character of no small part of the North 

 American flora. Following up some ideas which were touched 

 upon in this Journal (vol. xxxviii, Nov., 1884, p. 340) and else- 

 where, Mr. Ball writes : — 



"When we consider that, although subsidence has probably at 

 various times separated the two portions of the continent, the 

 highlands of Mexico and Central America have, in all probability, 

 served during long periods as a bridge over which some portions 

 of the mountain vegetation may have been transferred from North 

 to South, and vice versa, we are led to feel surprise rather at the 

 separations now existing than at the presence of many genera and 

 of a few identical species in the flora of the Andes and that of 

 the Rocky Mountains. It is true that I have reckoned as Andean 

 genera and species many that extend northward as far as Mexico ; 

 and it may well be that that region, so rich in varied forms of 

 vegetation, is the original home of some that now appear to be 

 more fully developed in the mountain ranges of Western North 

 America. Among the wide-spread American types we must note 

 two natural orders whose original home may with some confidence 

 be placed in the northwestern part of the continent. The Pole- 

 moniacece, of which about 140 species belong to that region, are 

 represented in the Andes by five species of (xilia, one of Collonia, 

 and by the endemic genus Cantua. They have sent to the Old 

 World two or three species of Phlox in Northern Asia [we be- 

 lieve only one, and that not far over the border], and a single 

 emigrant which has reached Britain, — the Jacob's Ladder of old- 

 fashioned gardens, — which maintains a struggling existence in 

 several isolated spots in Europe. The other specially American 

 family is that of the Hydrophyllacece, of which 12 genera are 

 known in N. America, but which is represented in the Andean 

 chain by only four species of Phaceliay The Loasacem illustrate 

 the opposite course of migration. 



A list of the plants which Mr. Ball collected in the upper valley 

 of the Ritnac in the Peruvian Andes, with various annotations 

 and the characters of some new species, concludes the present 

 interesting contribution to Andean botany. We believe that a 

 second paper upon the subject may be expected. Two or three 

 comments upon individual plants of the list will bring our review 

 to a close. 



JErodiuin cicutarium. — Although Mr. Ball notes the wide dif- 

 fusion of this old world species in South America, and that it 

 attends the distribution of cattle, he seems at a loss to account 

 for its presence in the Peruvian Andes at the height of 12,500 



