110 Coville : The Home of Botrychium pumicola 



bore ale. In general makeup and particularly in the form of the 

 lobes of the frond it resembles lunaria, indeed it bears a striking 

 resemblance to such an aberrant ternately divided specimen of 

 lunaria as is figured by Milde in his Gefass-Cryptogamen.* In the 

 series of thirty-one specimens of our plant preserved in the National 

 Herbarium, however, the ternate character of the sterile segment is 

 constant, except in a few depauperate plants in which the segment 

 is only a few millimeters in length. In pumicola the three divisions 

 of the sterile segment are ovate-triangular in outline and the lobes 

 uniformly imbricated, the lower and larger lobes are frequently 

 lobulate, or sometimes even pinnatifid and the entire sterile segment 

 is congested to a maximum length of 3 cm. In lunaria the sterile 

 segment has a single division, triangular-lanceolate in outline, its 

 lobes little or not at all imbricated and seldom distinctly lobulate, 

 the whole sterile segment often reaching a length of 5 or even 10 

 cm. In general configuration pumicola closely resembles horeale, 

 a resemblance chiefly due to the deltoid-ovate outline of the sterile 

 segment of boreale, but the latter has rhomboidal instead of lunate 

 lobes, and although these show a tendency to lobulation, they have 

 not developed to such a conspicuously greater extent than those 

 immediately above to give the frond a really ternate character. 

 From both borcalc and lunaria the present species differs in its very 

 pale green glaucous color, the much more persistent stem-sheaths, 

 and the fact that the stems are buried in the soil up to the point of 

 separation of the two segments. All of these are xerophilous 

 characters correlated with the remarkable habitat of the plants 



The soil of Llao Rock, a fine pumice gravel, apparently without 

 any admixture of humus, is covered in winter by probably ten feet 

 of snow. After this melts away in spring, the soil becomes very 

 dry, and as July and August are almost rainless the plants of this 

 and similar areas are subjected to an annual drouth of several weeks' 

 duration. While the elevation of this spot is very near timber 

 line, where the flora would normally be made up of circumpolar 

 plants, not a single such plant is found there. The species found 

 on the area are follows : 



Sitanion elymoides Raf. 



*• 



* Milde, Nov. Act. Acad. Leop. Car. 26 2 ; pi. 47 . f % ,25. 1858. 



