488 GrRiIGGs: THE SUGAR GROVE FLORA 
than in areas. For by this method: no locality can be possibly 
assigned to more than two zones whereas the flora of most regions 
is composed of numerous groups of plants of diverse affinities. 
The adequate representation of these requires not one but many 
maps each portraying a typical range. In the present paper an 
attempt is made to treat the Sugar Grove flora in this fashion.* 
It is however very difficult to secure the data necessary for 
a consideration of plant ranges and the results are necessarily 
crude in consequence. There has been as yet almost no exact 
research into the ranges of North American plants. Only in the 
case of a few specially interesting species has any great effort been 
* made to ascertain the facts of distribution. The ranges assigned 
to our plants in the manuals, even the most careful of them, are 
to a considerable extent the result of tradition and guesswork 
and are frequently far from accurate, while in works like Hough’s 
Trees, which is almost the only general work that has attempted 
to map ranges, the maps given are so inaccurate as to be almost 
useless for detailed work. The importance of reliable data of this 
sort may be brought out by an example. The chestnut, Castanea 
dentata, whose distribution is much talked of just now in estimates 
of the probable damage to be expected from the chestnut blight, 
Endothia parasitica, is usually given} as occurring over all of Ohio 
except the extreme northwest corner and much of Indiana. But. 
in realityt it is confined to the vicinity of the Lake Shore around 
the western end of Lake Erie, is entirely absent from western Ohio 
but occupies eastern Ohio and stretches through the southern part 
of the state into southern Indiana—thus lessening the area 
susceptible to damage by the blight by something more than 
10,000 square miles. 
The labor involved in determining accurately the: range of a 
single plant is not inconsiderable. There is not a single herbarium 
13: 135-162. Ig1I. 
+See map opp. p. 28 in Rep. Pennsylvania Chestnut Blight Conference. 
Harrisburg, 1912. f 
map opp. p. 180, I. c. 
