STUDIES OF THAUCTRACEAE — II. 91 



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belong to alpine summits of various and widely separated arid 

 regions from Colorado to California. They all differ from 

 T, alpinum of Wales, Scotland and eastern Canada in having 

 a more coriaceous foliage that in none is green above, but is 

 almost white-glaucous on both faces. The marks by which 

 they differ among themselves might in several instances be 

 considered varietal rather than specific were they all from the 

 mountains of Colorado, or all from those of Utah and Nevada, 

 or all from those of middle and southern California. But, 

 knowing as I do how extremely different the climatic condi- 

 tions are between either the Rocky Mountains of Colorado, or 

 those of Utah and the White Mountains of southern California, 

 and by how many hundreds of miles they are sundered from 

 each other in space — how completely isolated each type is, 

 and for ages has been — I reasonably hold these forms to be of 

 higher rank than those occurring within the small and climat- 

 ically uniform district of the islands and peninsulas of 

 eastern Canada, where I have found real T. alpi?inm to exist 

 in four distinguishable varieties.* 



Thai^ictrum SCOPUI.ORUM. Plants not tufted, often soli- 

 tary, usually 3 to 7 inches high, the scapes wiry, floriferous 

 from below the middle, the leaves short-petioled and spread- 

 ing, or at most ascending : leaflets very small, usually 11 to 

 the leaf, coriaceous, both faces glaucous, yet the upper some- 

 what lustrous, also marked with white veins that are continu- 

 ous from base to and through the lobes, these very obtuse, 

 also the sinuses mostly closed, the lobes meeting or even 

 overlapping each other : pedicels slender, not greatly elon- 

 gated even in fruit, curved downwards throughout their 

 length : sepals ovate-oblong, acute : anthers almost linear, 

 long-pointed, or at least acute: carpels few, oblong-obovate, 

 rather strongly ribbed, sessile. 



Common on rocky and bleak alpine summits of the moun- 

 tains of Colorado, a good type being Hall and Harbour's n. 



' Cf . Ottawa Naturalist, xxiii, 17-19. 





