Harshberger: Plant formations of Nockamixon Rocks GfiO 



by Afnelanchier canadensis, Rnbus canadensis, R. hispidns, R. 



( 



pubcscens, Pop 



iifoUus^ Bapt. 



tinctoria, and Sedum Telephiurn {S. piirpiu'cuni). The lianes begin 

 their growth on a shelf, or in a rock pocket and ascend the cliffs, 

 as if directed on a treUis. Such are Ampelopsis qidnquefolia^ Vilis 



'difolia 



Near the top of the cliffs on some 



shelves (figure 5) sheltered by the overhanging rocks and asso- 

 ciated with Cajnpamda rotttndifolia, Anemone poinsylvanica, Chelone 

 glabra^ Steironcma cdiatnvi, Salix cordata, PJiysocarpus opulifoliiis^ 

 Maia7it]ienmm canadcnse^ Poljpodimn vulgare, and Geranhivi 

 Robertiamun, grows the most unique plant of the Nockamixon 

 Rocks, viz., Sedum RJiodiola (5*. rosettni). This plant, which 

 grows on the bare shale rock, is anchored by thick, succulent, 

 coral'Hke, branching rhizomes, which giv^e rise \n summer to the 

 grayish green leaves and small yellow^ish green flowers. Each 

 season the leaves fall from the plant, and the bare rhizomes, with 

 the additional annual growth, perennate until the next growing 

 season. The writer measured one plant with a rhizome six 

 inches long and with roots that penetrated the rock crevices over 

 two feet. This plant is perhaps most abundant beneath the shelv- 

 ing rocks at the head of one of the ravines, which Is kept cool by 

 the currents of air which strike the rocks in such a direction as to 



+ ^ 



be deflected into the rocky amphitheater at the head of the glen, 

 where the roseroot grows so abundantly. On several hot days 



last summer, the temperature was perceptibly lower In the shadow 

 of the beetling cliffs, fanned by the breezes, which blew into the 

 glen from the north. In all probability, Sedum Rhodiola (5. 

 rosetwt) IS a relict of the time when the climate was much colder 

 than now — a time characterized by the retreat oi the glacial ice 

 sheets that covered the headwaters of the Delaware River. The 

 present distribution of the plant supports this view, because it 

 occurs in Greenland and Labrador, on the high alpine peaks from 

 Alberta and Alaska to Colorado and California (altitude 9.000- 

 14,000 feet), also along the coast to rocky islands and cliffs in 



Maine 



Tervis, Wayr 



* Cushman, Joseph A. Some interesting Maine plants. Rhodora ii : 12. 1909. 



