42 T. Holm — Studies in the Cyjperacem. 



and iS^ortli America, but is much more frequent farther South. 

 AVe have called attention to the occurrence of C. melanocephala 

 in the mountains of Colorado, where C. alpina also occurs, 

 and we have mentioned the presence of two types, which we 

 consider as allies of C. atrata : C. hella and C. chalciolepis^ as 

 inhabiting these same mountains together with G. atrata. 

 Furthermore that a third ally of C. atrata, C. ovata, abounds 

 in the northeastern parts of this continent, thus illustrating 

 the occurrence of allied types associated with each other, 

 which we believe might indicate the location of the center of 

 distribution as being in the Rocky Mountains, as far as con- 

 cerns the American representatives of C. atrata and alpina. 

 We have stated, moreover, that C. atrata is in Europe, to some 

 extent, accompanied by two plants C. nigra and aterrhna.^ 

 both of which may be looked upon as immediate allies of this 

 species. And if we extend our comparison of these species 

 with those that occur in the Himalayas, we iind there not only 

 typical C. atrata and alpina, but also some aberrant forms, 

 and some distinct species, among which C. Lehmannii, ohscura, 

 Ditthiei, nivalis, and psychrophila, which appear to represent 

 immediate allies of these two species. If thus the association 

 with allies in connection with frequent occurrence and tendency 

 to vary may throw any light upon the question as to their 

 center of distribution or even of development, we believe we 

 are justified in supjDOsing that as far as we know C. atrata and 

 C. alpina in this particular respect, these species had probably 

 more than one center, and very likely one in the Kocky 

 Mountains, another in the European Alps and a third one in 

 the Himalayas. 



The third and fourth category of Northern types emphasize 

 such species as are not arctic ; only a very few of these are 

 alpine ; C. petasata, Bonplandii ?ca& filifolia, and these are, fur- 

 thermore, endemic to the Kocky Mountains. The remaining 

 species of these same categories are either common to both 

 worlds or endemic to North America and some to the Kocky 

 Mountains alone. Carex stelhdata is widely distributed through- 

 out the northern hemisphere in the lowdands of the temperate 

 zone ; besides that, it occurs in New Zealand. It reaches its 

 highest development on this continent, where it exhibits a vast 

 number of forms, some of which have been segregated as dis- 

 tinct species and is, in the northern provinces, frequently 

 associated with an ally, C. gynocrates, which we consider as 

 representing a forma liebetata of the section Astrostachym. 

 C. gynocrates does not seem to occur in Siberia, but its hom- 

 ologue, C. Redowskyana, has been reported from several stations 

 of that country, where, however, C. stellulata is absent, at 

 least in the northern parts. The European C. stellulata shows 

 no tendency to vary, but the fact that it is associated with such 



