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Harshberger : Plant formations of Nockamixon Rocks 663 



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the river, these rocks suggest the well-known Palisades of the 

 Hudson River, but their color and origin are different, as they are 

 composed of red shale. From this distance, the cliffs seem to be 

 unbroken and higher than actual measurement indicates. The 

 vegetation from the opposite bank of the river appears confined to 

 the talus and the upper more gradual slopes near the crest of the 



cliffs. A 



in addi- 



tion the botanist notes that every ledge, shelf, and crevice is occu- 

 pied by trees, shrubs, and herbaceous plants which grow either in 

 the bare rocky soil or 'where a poor soil has been formed by the 

 disintegration of the rock masses (figure 4). Viewed from the 

 towpath of the canal at the base of the cliffs, the impression is that 

 of a mixed deciduous forest with clumps of hemlocks, here and 

 there, or a facies of the red cedar {^Jiuiipertis virgiiiiand) to break 

 the more even crown of the broad-leaved forest trees. Back of 

 the cliffs the forest has been cleared and the nearly level surface 

 is devoted to the cultivation of the ordinary farm crops. Beyond 

 the fields to the south rises a group of rounded hills, ranging from 

 600 to 780 feet, the highest point being three quarters of a mile 

 south of the edge of the rocks. A canal and a dirt road occupy 

 the shore between the lower edge of the talus and the river bank 

 (figure 2). The talus, which is considerable at the west end, but 

 almost absent in the middle and at the east end, consists of ex- 

 tremely loose broken pieces of the shale rock. It is difficult to 

 climb over such material, because it constantly slides from beneath 

 the feet, -The mass of rock is a hard red slate, but the edges of 

 the rock-shelves break off only too easily, as the climber finds out 

 in attempting to ascend from shelf to shelf by his hands and knees 

 (figures 4 and 5). Care must be exercised not to lay hold of a piece 

 that breaks away from the cliff. Numerous cracks appear in the 

 rocks following the natural cleavage-planes, so that the rock soil 

 and talus material is extremely porous, permitting the rapid per- 

 colation of the rain-water, which, when it first falls, makes the soil 

 and rocks extremely slimy and slippery. Such a substratum upon 

 which the characteristic plants of the locality are found growing 

 is noted for its physiologic dryness, which is especially noteworthy 

 in the summer, when little rain falls, and yet it is surprising what 

 a large number of plants will grow and carry on their life proc- 



