198 Rhodora [Octohkr 



minor (the European associate of /'. rofiifidi/olia), a species occurring 

 in arctic and subarctic America, extending southward in cold tir and 

 spruce forests and deep swamps to Cape Breton, the higher moun- 

 tains of northern New England, the Great Lakes, and the Rocky 

 Mountains. At no point, except possibly the extreme northern limit 

 of P. rotundifolia and the extreme southeastern limit of P. minor 

 (where each species is rare and local) do their ranges coincide ; and 

 nowhere in America, so far as known, has there ever been found any 

 transition between the two species, such as is represented in Europe 

 by P. media. 



Superficially the three plants, the European Pyrola rotiindi/olia, the 

 Arctic P. grandifiora, and the so-called P. rotundifolia of temperate 

 America, present little to indicate that they may not be phases of one 

 broadly distributed species ; and as such they have been treated by 

 many authors, who, at the same time, have included with them P, 

 asarifo/ia, Michx. and /'. bradeata, Hook., both species of well 

 defined characters and geographic range. In general, the plant of 

 temperate North America is taller and has larger leaves, while the 

 Arctic /'. grandiflora is lower and with smaller leaves than P. 

 rotundifolia of Europe.^ In general, too, P. grandiflora of the 

 Arctic regions and the plant of the eastern United States and Can- 

 ada have much larger flowers with thicker petals than the European 

 species, but in plants from northern Scandinavia the corolla is as 

 large as in average American specimens.'^ 



A comparison of the stamens brings out certain points which indi- 

 cate, even more than the geographic range and the variation in size 

 and texture of the petals and the size of the leaves, that the three 

 plants are probably best treated as distinct species, or at least as 

 well developed geograpliic subspecies. In the large-fiowered plant 

 of the eastern United States and Canada the filaments are shorter 



1 Measurement of 50 American herbarium-specimens shows a range in height 

 from 9 to 36 (average 25) cm. ; of 28 European plants a range from 15 to 30 (aver- 

 age 2d) cm.; of 25 Arctic plants a range from 5 to 16 (average 10) cm. The 

 leaves of the American plants show a range in the length of blade from 2 to 6.8 

 (average 4.4) cm. ; of the P^uropean from 1.9 to 4.6 (average 3.3) cm. ; of the 

 Arctic from i to 3 (average 2) cm. 



" Petals of 20 herbarium specimens of the plant of temperate America vary in 

 length from 6.5 to 10.5 (average 8.4) mm.; of 20 European specimens tkey vary 

 from 5.5 to 8 (average 6.5) mm.; of 20 Arctic American plants from 7.5 to 11 

 (average 8.7) mm. 



