M4 THE SELAGINELLA RUPESTR1S GROUP. 



elevated regions and is found only in the West. It has 

 been reported from various peaks in Utah, Nevada, and 

 California, always at altitudes above 5,000 feet. A form 

 very similar to this, but differing in having about eight 

 cilia on the leaf-margins and no awn tips to 

 the leaves, has been described as a species 

 under the name of Selaginella niutica. The 

 fact that the sporophylls usually have a short 

 awn-tip seems to indicate that it is a form of 

 Selaginella Watsoni, and this is further borne 

 out by its habitat in the mountains of Colo- 

 rado, New Mexico, and Arizona. We would 

 therefore call it Selaginella Watsoni unit iea, and 

 give its range as high mountains from Colorado 

 to New Mexico and California. 



(Enlarged.) 



"The Sand-Barren Selaginella. 



It is almost certain that the sand-barren selacinella 



o 



(Selaginella arenicola} and the common species of the 

 Northeastern States, sprang from the same stock ; 

 but the former has lived so long in the sandy wastes 

 that border the Gulf of Mexico that its appearance has 

 been greatly changed in consequence. Possibly there 

 may yet be found intergrading forms, but the typical 

 plant is so distinct in appearance that it is properly con- 

 sidered a separate species. This species is an excellent 

 illustration of the adaptation of plants to their surround- 

 ings. It grows in exposed sandy places, and accordingly 

 its leaves are narrow, plentifully ciliated, and appressed 

 closely to the stem, partly in an effort to avoid excessive 

 transpiration, and partly, no doubt, to protect its green 

 cells from the strong light. 



