10 



In outlining the range of each species care has been taken, when- 

 ever reliable information was available, to indicate as exactly as possi- 

 ble points of limitation by the mention of counties, water courses, 

 mountain systems, etc., and especially has this been aimed at in the 

 case of new, rare, or little-known species. Wherever the range appears 

 in more general terms specific information has not been at hand with 

 which to give more definite limits. In the case of very common, 

 widely, and continuously distributed species, however, the range often 

 appears in somewhat general terms, for the reason that the ready 

 detection of the species within the general lines renders more detailed 

 delineation unnecessary. 



A lack of space has excluded from the present catalogue any but 

 occasional statements of the manner of occurrence of each species, 

 that is, whether found in forests of pure growth, as in the case of 

 Beech, Sugar Maple, White Oak, White Pine, etc., or as single indi- 

 viduals or scattered groups in a mixed growth, as is the case with the 

 magnolias, basswoods, ashes, etc. Related and alike interesting facts 

 which have been omitted are the special characters of soil, moisture, 

 and altitude appearing to limit the natural occurrence of individuals 

 to certain sites within a species' broader range; as, for example, the 

 exclusive occupancy of low, mucky ground in the Xortheast by the 

 Tamarack, while the adjoining stififer soils may bear Black Ash. with 

 Red Maple and Yellow Birch, and the still drier contiguous upland 

 soils may bear Red Oak, White Oak, Sugar Maple, etc. 



Again, man}' trees are found to be more or less continuously distrib- 

 uted throughout their range, so that they are likely to be met with at 

 frequent intervals. Thus, in traversing the territorial range of the 

 familiar White. Oak, individuals may be found in nearly every county 

 and township, while less common species will be met with only in more 

 widely separated stations, in some cases occurring a^ apparently acci- 

 dental individuals. Peculiar, but usually accountable, phenomena are 

 also seen in tree distribution where extensive areas of forest forming 

 species are very widely disconnected. A familiar example of this is 

 the distribution of Pinus palustris iu the Gulf region, where the species 

 suddenly fades out east of the Mississippi River, but reappears again 

 and in commercial quantities about 100 miles westward, in eastern 

 Texas. Other less marked examples might be cited. 



It is, therefore, to be understood by the layman that within the ranges, 

 as stated in general terms, the species may be absent in many locali- 

 ties, and personal observation must aid the student to properly inter- 

 pret the general range. 



ADVENTIVE TEEES. 



In enumerating the indigenous trees of North America, it seems proper 

 from time to time to include also certain exotic species which show the 

 power of existing and spreading independently and without cultivation. 

 Occurrence under such conditions may be taken as fairly indicative of 



