T. Holm — Studies in the Cyperacecu. 283 



Uiriculus. 



The anatomical structure of this little organ appears to be 

 very uniform in these species of the Stenocarpw ; it is very 

 thin on account of the very little mesophyll, which forms here 

 only one stratum between the two mestome-bundles, while it 

 may be represented as two or three in the immediate vicinity 

 of these. The outer wall of epidermis, on the dorsal face, is, 

 however, thick in these species, while that on the ventral face 

 is invariably very thin, like the radial walls. Stereome is also 

 developed in the utricle of these species, but it is not very 

 thick-walled and does not occur in groups of any considerable 

 size either; it accompanies the two mestome-bundles, and it 

 occurs besides as isolated groups between these, but not in all 

 the species. In G. misandra and C.frigida the stereome was 

 restricted to the mestome-bundles, but in the other species we 

 found from 5 to 14 isolated groups between these ; the utricle 

 of C. brachystachys and C . ferrxiginea appear to possess the 

 strongest mechanical support of these species. 



In comparing these anatomical details of the Stenocarpos, the 

 species examined seem to possess a very uniform structure in 

 spite of the fact that they were collected from very remote 

 stations, Alaska, Colorado, Middle-Europe and the arctic region, 

 and in the case of C. misandra, the specimens from Alaska 

 exhibited the same anatomical characteristics as those from the 

 alpine slopes of Rocky Mountains (Colorado) and Switzerland 

 besides from the arctic region. The internal structure consid- 

 ered by itself is very much in conformity with that of a num- 

 ber of arctic plants of various orders which we have had oppor- 

 tunity to examine, and which seems to indicate that these 

 species lived under conditions that were influenced by a moist 

 rather than by a dry atmosphere. The development of the Steno- 

 carpw seems thus to have taken place, at least, in recent time, 

 in alpine or boreal regions, where they are yet in existence, 

 and if we combine the geographical distribution, including the 

 nature of the surroundings, with the external and internal 

 peculiarities of these Carices, we see no objection to consider 

 C. circinata and C. lejocarpa as "forme® hebetatce " of this 

 section. 



Brookland, D. C, April, 1900. 



Am. Jour. Sci.— Fourth Series, Vol. X, No. 58. — October, 1900. 

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