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the east side. But most of my investigations and collections have 

 been made along the river-banks, near my residence, or, as the title 

 expresses it, in the "Highlands," — a section of the river-valley ex- 

 tending north from Kidd's Point, or Caldwell's Landing, for a distance 

 of twenty miles. 



The mountain slopes are thickly wooded in most places, but in the 

 rocky soil the deciduous trees seldom grow to a very large size. The 

 river slopes are, for the most part, thickly clothed with coniferous 

 trees, affording food and shelter for the winter residents. The follow- 

 ing list of Coniferce belongs to our flora : — 



Pinus rigida, Miller. Pitch Pine. 



Pinus strobus, Linne. White Pine. 



Abies canadensis, Michx. Hemlock. 



Thuja occidentalism Linn6. American Arbor Vitse. 



Juniperus communis, Linne. Common Juniper. 



Juniperus virginiana, Linne. Red Cedar. 



Taxus baccata var. canadensis. American Yew; Ground Hemlock. 



The Hudson River constitutes a natural channel, through which the 

 tide of semi-annual migration always pours with more than ordinary 

 vigor; and it also affords an avenue of approach for the numerous 

 aquatic species that visit us during the migrations, or remain here 

 during the summer. Hence many of the marine species visit us dur- 

 ing their migrations. 



Zoologists are familiar with the fact, that rivers are very important 

 factors in limiting or extending different faunae. It is known that a 

 given avi-fauua may be prolonged by them in streaks. This is a 

 demonstrable fact, and is equally applicable to other classes of ani- 

 mals, and even to the flora. Of the mammals, the common Opossum 

 {Didelphys virginiana) may be cited as illustrating this influence. This 

 species finds its northernmost extension along the west bank of the 

 Hudson. It also illustrates the restrictionary effect of rivers. The 

 Hudson interposes a barrier to the progress of the species eastward, 

 and, accordingly, it has rarely — never to my knowledge — been ob- 

 served on the east bank of the river, though it is not uncommon upon 

 the opposite side; occurring at least as far up as Newburgh. Among 

 the plants, I shall cite but a single species, the common persimmon 

 (Diospyros virginiana), which has also crept up the Hudson to a con- 

 siderable distance from the general northern boundary of its habitat. 

 DeKay wrote the following, in confirmation of the above-mentioned 

 facts, as long ago as 1844: "On the other hand, the Hudson River 

 appears to form a natural geographical limit to the extension of some 

 species, at least in any considerable numbers. Thus, the Opossum of 

 the South rarely, if ever, outstrips this boundary ; among the reptiles, 



