FLORA OF THE YELLOWSTONE NATIONAL PARK. 19 



parum, L.) ; Habenaria (H. hyperborea, R. Br. ; H. dilatata, 

 Gray) ; and Allium (A. Schcenoprasum, L. ; A. brevistylum, 

 Wats.). Among other characteristic species are Trifolium 

 longipes, Nutt. ; Pedicularis Grcenlandica, Retz. ; Rumex pauci- 

 folius, Nutt., and Zygadenus elegans, Pursh. Here, as elsewhere, 

 especially over the hot spring and geyser areas, the small 

 streams are bordered with Parnassia fimbriata, Banks ; Gen- 

 tiana serrata, Gunner, and Mimulus luteus, L. 



Among the water plants of the Park we find a few of which 

 the Rocky Mountain region is the eastern or western limit, but 

 by far the greater portion, at least 70 per cent, of the species, 

 extend across the continent. Water plants, from the more 

 uniform nature of their surroundings in water, which also is an 

 important factor in their distribution, would naturally have a 

 more extensive range than land plants, which over a large area 

 would be subjected to great differences in soil and climate. 



Of this flora of the ponds and streams we find Ranunculus 

 aquatilus, L., var. trichophylluSj Chaix., almost everywhere, and 

 R. multijidus, Pursh., more rarely about Yellowstone Lake. 

 Nuphar advena, Ait., is rarely absent from muddy ponds and 

 sluggish streams, and frequently associated with great quantities 

 of Hippuris vulgaris, L., and Ceratophyllum demersum, L. ; 

 Nuphar poly sepalum, Engelm., was collected only in the Gibbon 

 Lakes. Sparganium simplex, Huds., var. angustifolium, 

 Engelm. ; Sagittaria variabilis, Engelm., and Utricularia vul- 

 garis, L., though frequent, are rarely seen in flower or fruit. Of 

 the three Lemnas (L. trisulca, L. ; L. minor, L. ; L. gibba, L.), the 

 two former are extremely abundant in many localities. Several 

 Potamogetons (P. rufescens, Schad. ; P. gramineus, L., var. 

 maximus ; P. perfoliatus, L. ; P. pectinatus, L., and var. lati- 

 folius, Robbins), are common throughout in the lakes and 

 streams. Subularia aquatica, L., and Isoetes Bolanderi, Engelm., 

 are found on the bottom of ponds about Yellowstone Lake, the 

 latter species being pretty generally distributed over the region. 

 What is apparently the rare and local Isoetes pygmsea, Engelm., 

 has been found at Yellowstone Lake. Callitriche autumnalis, 

 L., is abundant, and less so C. verna, L. Besides these may be 

 mentioned Zanichellia palustris, L. ; Ruppia maritima, L. ; 

 Marsilia vestita, Hook and Grev. ; Myriophyllum verticillatum, 



