96 The Ottawa" Naturalist. [Nov. 



Polypodium vulgare L. (Common Polypody). Found on 

 the tops and upper ledges of rocks where the soil is well drained; 

 the usual shade -producing plants associated with it in this 

 habitat are poplar, paper birch, small hard maple and hemlock. 

 Also found rarely on clay banks where the soil contained a little 

 sand ; in this habitat it was practically unshaded as the slopes 

 were typical hemlock ridges. The plants under the latter con- 

 ditions were dwarfed, probably from lack of shade rather than 

 from the nature of the soil. 



Camptosorus rhizophyllus (L.) Link. (Walking Fern). 

 Is found usually in crevices in limestone and sandstone rocks, but 

 sometimes rooting in moss on narrow ledges. Appears 

 to prefer the shady side of the rocks, but thrives fairly well in 

 the sun. It is found in abundance on the rocks that cover the 

 clay slope at Credit Forks. 



Asplenium Trichomanes L. (Maidenhair Spleenwort), and 

 Asplenium viride Huds. (Green Spleenwort) are found rooting 

 in the crevices of shady rocks and cliffs; usuallv limestone or 

 sandstone. They are not sensitive to lack of moisture , but .4 . mri ie 

 does not stand exposure to the sun so well as the other 

 species. Both the ferns are associated at Credit Forks among 

 the talus on the clay slope. 



Aspidium Thelypteris (L.) Sw. (Marsh Fern). The ideal 

 habitat of this fern is decidedly wet, as it is found growing 

 usually with cat-tails. Shade is not an indispensable factor, but the 

 fern is sheltered when thriving best. The shade producers 

 are commonly cedar, black ash, soft elm, hemlock and occasion- 

 ally basswood. In moist situations, under full illumination, the 

 fern thrives and it will grow in a fairly dry situation 

 until crowded out by grasses and sedges. It shows a high degree 

 of plasticity in relation to the environment, more so than any 

 of our native ferns, unless perhaps Pteris. 



Aspidium noveboracense (L.) Sw. (New York Fern) 

 In direct contrast to the preceding .species, this fern is found in 

 dry soil, but always under dense shade in the typical '"cool 

 woods." It is very abundant in a woods near Lake Huron ; 

 there it is associated with partridge berry, pyrolas, and shaded 

 by birch, hemlock and maple. Maple and beech underbrush 

 were also important factors in shade production. As only a few 

 inches of humus was covering a somewhat impervious substratum 

 of sandy loam, sufficient moisture was ensured. The rootstoeks 

 of the ferns did not penetrate below the humus. In mucky parts 

 of the same woods Polystichum acrostichoides and Aiiantuin 

 pedatum were associated with this fern. 



