BARBERRIES. 795 



When once the good services of birds had been secured, there 

 would be no need of having so many seeds in each fruit as must 

 have been formerly necessary to compensate for the extreme 

 wastefulness of wind as a distributing agent. At the same time 

 a reduction in the number would permit, as we have already had 

 occasion to notice, a higher development of each remaining seed 

 that is to say, an increase of reserve food and a thickening of the 

 outer coat, features that we find to vary directly as the number of 

 seeds, there being all the way from eight (in many mahonias) to 

 two or even one in the true barberries. 



However the characteristics of the barberry fruit may have 

 arisen, the fact that they came to depend upon birds for their dis- 

 semination must have exerted an important influence upon all the 

 subsequent differentiation of the group, for barberries were thus 

 brought into widely separated regions which they might not 

 otherwise have reached and so came to grow up in widely differ- 

 ent surroundings. 



We have already considered the extent of the migrations which 

 are believed to have taken place in preglacial times. Among the 

 forms which became adapted to the refrigerated climate that 

 heralded the Glacial epoch, one of the most successful was prob- 

 ably a form almost if not quite identical with the modern Berberis 

 canadensis, which despite its name does not grow in Canada, but 

 is found only in the Alleghanies of Virginia and southward. 

 Before the glacier came, however, the ancestral form we are speak- 

 ing of probably did occur even to the north of Canada, and through 

 the agency of birds was carried into Asia and distributed widely 

 on that continent. Under the influence of their new environment 

 it would not be strange if in the Asiatic descendants of the cana- 

 densis stock there appeared, even during the (geologically) short 

 time since the beginning of the Glacial period, those slight differ- 

 ences which now distinguish Berberis vulgaris from the American 

 descendants differences which in the minds of some botanists en- 

 title the two forms to rank only as varieties of the same species. 

 After the retreat of the glacier, Berberis vulgaris extends into 

 Europe to take the place of the mahonias previously extermi- 

 nated. It now flourishes from England to Persia and from Persia 

 to Japan. Our forefathers bring the plant to this country (largely 

 for the sake of its fruit), and thus it finally returns to the ances- 

 tral acres. It would surely seem to be not a little invigorated by 

 its journey around the world, since in the acquisition of American 

 territory it appears to be in a fair way to outdo its stay-at-home 

 relative, and has already fully justified with us its Old World 

 name of " common barberry/' 



[Concluded. ] 



