642 Rydberg: Phytogeographical notes 



forming often large fields of deposits in the form of crusts, which in 

 course of time often become broken up and form sand fields. 

 These hot spring formations have a peculiar flora of their own. 

 The grasses are not many, however, but at least two of them have, 

 so far as the writer knows, never been found elsewhere. These 

 are Panicum thermale and Deschampsia pungens. The former 

 has been collected also around hot springs in California. 

 Besides these Spartina gracilis and Pa?iicum barbipulvinatum are 

 common. These are plants from the Great Plains, the former 

 frequent in alkaline meadows and the latter in sand-draws. 

 Another plant although not a grass, but a sedge, may be mentioned 

 here, viz. Eleocharis thermalis, growing in the pools below the 

 springs with water even too hot for a comfortable bath. 



10. RuDERAL Regions 



A few of the ruderal grasses of the Great Plains and the regions 

 east thereof have been found near dwellings, along roads, in fields 

 and in waste places as high up as within the limits of the Montane 

 Zone. These are: 



Synthyrisma humifusum Chaetochloa glauca 



Panicum capillare Polypogon monspeliensis 



" harhipidvinatum Avena fatua 



Poa annua Bromus hordeaceus 

 Dactylis glomerata " secundus 



New York Botanical Garden 



