2 



THE FERN BULLETIN 



sandstone rocks. It was a small colony, the few- 

 straggling stems presenting an appearance quite dif- 

 ferent from the nests or bunches one commonly finds 

 when it grows on limestone. Again, in the summer 

 of L910, w hile spending a week studying the flora in 

 the Dells of the Wisconsin river, near Kilbourn, Wis., 

 I saw the cliff brake but once, a small bunch similar to 

 the one at Oregon. The rock of the Dells is the Pots- 

 dam sandstone. Once before, in 1893, I took it from 

 the sandstone cliffs bordering Lake Mendota, Madison, 

 Wis. A note made at the time simply gives sandstone 

 cliffs, but does not state whether the plants were grow- 

 ing on the Potsdam or the Madison sandstone, a name 

 applied to a thinner bed in which more calcareous 

 matter is mixed with the ferruginous than is the case 

 with the cementing material of the Potsdam. The 

 bearing of this will appear later on -in the discussion. 

 Attention is called to these facts since the common 

 habitat of both the Pellacas is stated to be limestone, 

 or calcareous rocks, implying that lime is the principal 

 ingredient. Gray's New Manual for P. atro purpurea 

 specifies "dry calcareous rocks" only, and for P. 

 gracilis ( Crypto gram ma Stelleri), "shaded chiefly 

 calcareous rocks," thus according the latter a wider 

 edaphic range. The statements in books that give habi- 

 tats vary in regard to the ferns, but the more common 

 one, as agrees with experience in general, is cal- 

 careous rocks. 



In view of these facts and statements, it is well to 

 examine the case more closely and see what are the 

 edaphic and other ecologic relations of the two cliff- 

 brakes. They are characterized in one of their 

 features as growing on rocks. This may not neces- 

 sarily mean that they are true lithophytes, or rock- 

 plants, with rock as the sole substratum, but such is 



