T. Holm — Studies in the Cyjperaceoe. 43 



species as C. diceca and DavalUana. both of which appear to 

 represent lower types of the section {Astrostachym)^ makes us 

 believe that there is both an American and an European center 

 of its distribution and development. Carex tenella shows 

 a similar wide distribution on this continent from the 

 Atlantic slope to Alaska, associated with such near allies as C. 

 canescens^ loliacea^ tenuiflora^ etc., all of which are, also, known 

 from Scandinavia ; hence we might conclude that they originated 

 from two centers, one in Scandinavia and another one in the 

 northern Rock}^ Mountains. 



Among the species of this category, which we suppose were 

 developed in the Rocky Mountains, but which took part in the 

 migration northward with the arctic plants on their return, may 

 be mentioned G. pratensis, of which the very isolated occurrence 

 in South Greenland does not seem explainable in any other way. 

 The almost cosmopolitan C, vidgaris is difficult to locate, inas- 

 much as it is generally accompanied by several allied types, 

 wherever it occurs in the mountains or lowlands. We can only 

 say that it does not belong to the arctic region, and that the 

 diversity of types into which it has developed, for instance in the 

 Himalayan Mountains, in Scandinavia and in the northwestern 

 parts of this continent, indicates several local centers. 



In regard to the other types, the majority of these are 

 endemic to I^orth America and several to the Rocky Moun- 

 tains, where they have, naturally, developed. 



The second category, "Southern types," contains a few. 

 species common to both worlds, among which C. pyrenaica 

 shows a remarkable wide distribution : from Colorado to the 

 British provinces, Alaska, the Pyrenees and Alps of Swit- 

 zerland, Caucasus, Japan and J^ew Zealand, while its nearest 

 ally C. nigricans is confined to the Rocky Mountains and Alaska 

 and C. macrostyla to Spain and the Azores. C.foetida is only 

 known from Colorado, California and the Alps of Switzerland. 

 C. stenophylla follows the Rock}^ Mountains throughout 

 Canada, and is known also from Southern Europe, Caucasus, 

 Altai, Bajkal, Himalayas and China. The geographical center of 

 0. nigricans may, beyond doubt, be sought in the Rocky 

 Mountains, while it seems impossible to locate that of C. 

 pyrenaica, unless there may have been at least two centers, 

 one in the Rocky Mountains and another in the old world, 

 Europe or Asia ; its occurrence in JS'ew Zealand can not be 

 accounted for with any satisfaction. In regard to C. foetida 

 we feel unable to explain its distribution in any other way 

 than by admitting two centers, the Rocky Mountains and Switzer- 

 land Alps. And if we consider C. stenophylla, there seems no 

 possibility of defining its center with any proximity neither in 

 this country or in the old world. 



Among the southern types that are endemic to this con- 



