THE SELAGINELLA RUPESTRIS GROUP. 



145 



The stems, under the influence of the intense insola- 

 tion, are nearly erect, but seldom become more than two 

 inches high. They are densely tufted, much branched, 

 and form compact little mats on the sand. From the 

 part nearest the earth, slender branching roots descend 

 into the soil, and in the search for moisture extend for 

 long distances, being often three times the length of 

 the aerial parts of the plant. The leaves are smaller 

 than those of any of our other selaginellas, and those on 



the sterile stems are 

 not distinguishable 

 -. from one another by 

 I; the unaided eye. 

 Under a lens they 

 are seen to be very 

 narrow, with a whitish 

 awn at the apex and 

 many minute cilia on 

 ., y// the outer edges, while the usual channel 

 runs lengthwise of the outer side. They 

 are thickly clustered on the stems and 

 branches, and so closely appressed that 

 stem and leaves combined have a diam- 

 eter of about a thirty-second of an 

 inch. The fruiting-spikes are very 

 numerous and terminate the ends of 

 ) ",\, the branches. Although the whole 

 SAMD-B\RREN SELA- P''"^"' '^ usually Under three inches 

 GixELLA. 1^- 1^ these fertile spikes may reach a 



Seuigmella arcJitcola. ^ •' 



length of an inch or more. They are 

 sharply four-angled, with a diameter somewhat greater 

 than that of sterile branches. The sporophylls are much 

 larger than the leaves and are borne in four closely 



