narrower unit than in related genera and was based upon less 
significant differences in botanical characters. According to later 
studies, most of these numerous binomials apparently designate 
minor variations (“apomictic segregates”) derived from hybridiza- 
tion and propagated vegetatively by seeds without pollination. 
The compilation of Crataegus in the Forest Service Check List 
(Little 1953) listed 140 additional eastern species and mentioned 34 
others in notes, following treatments by specialists in floras. Later 
manuals have accepted far fewer species (or species groups). For 
example, Gleason and Cronquist (1963) reduced the number for 
Northeastern United States to 24. For North and South Carolina, 
Radford, Ahles, and Bell (1968) recognized and mapped only 13. In 
Texas, Correll and Johnston (1970) accepted 33. 
Lack of uniformity in species concepts, especially from one State 
to another, obviously restricts the value of maps in Crataegus 
compiled from herbarium labels. Also, coverage varies in detail and 
may be irregular or spotty by localities. As in any large genus, 
identification is difficult. For Ohio, Braun (1961) attempted to plot 
by counties 6] native species. 
Perhaps the populations of hawthorns (Crataegus) native in 
Eastern United States could be arranged or “lumped” for practical 
study into a workable number of about 25 to 40 species or species 
groups. Then distribution could be compiled, first by presence or 
absence in each State. Meanwhile, the eastern species of this genus 
are omitted. 
The 166 species of minor eastern hardwoods (including 4 of 
monocotyledons) mapped in this volume are grouped within 75 
genera and 41 plant families. A botanical index of genera and 
families appeared in the Check List (Little 1953, p. 445-450). Totals 
are incomplete, because important hardwoods are in Volume 1. 
Largest genera in Volume 4 are: cherry—plum (Prunus), 11; holly 
(Ilex), oak (Quercus), and willow (Salix), 10 each; and dogwood 
(Cornus) and viburnum (Viburnum), 6 each. Combined with Volume 
1, the largest genera of eastern hardwoods are: oak (Quercus), 31 
species; cherry—plum (Prunus) and willow (Salix), 12 each; hickory 
(Carya) and holly (Ilex), 11 each; and maple (Acer), 9. 
PREPARATION OF THE MAPS 
The maps in this volume have been compiled from various sources, 
following the procedure explained in previous volumes. Principal 
records on tree distribution include publications, herbarium speci- 
mens, field work, and review by botanists, foresters, and others. The 
more detailed publications consulted are listed under Selected 
References (p. 15). Credit is due many persons for their valuable 
assistance. The list of publications and persons consulted is too long 
for citation here. Naturally, the compiler is responsible for all errors. 
Publications with information about tree distribution have been 
examined for each State. Tree guides and similar books for 
identification have been compiled in a recent bibliography (Little 
and Honkala 1976). State floras, manuals, and catalogs have been 
consulted. 
References for several States summarize tree species distribution 
accurately and in detail almost as precise as maps, such as by 
counties or counties along the border or, for rare species, by 
localities. In other States, scattered published local floras with lists 
by counties or similar geographic units have been helpful in filling 
the gaps. The classic Manual by Sargent (1926) contains important 
locality records. Notes on range extensions are found in various 
scientific periodicals. Several unpublished theses with maps or other 
distribution records have been examined. 
Published maps have been valuable sources in this compilation. 
Altogether, more than one-fourth of the States now have publica- 
tions with distribution maps of all or most native tree species, as 
noted in the first volume (Little 1971a, p. 5). These, with author 
and year, for 12 of the 37 Eastern States of this volume, are: 
Alabama (Clark 1971); Georgia (Harper 1907-08; Duncan 1950); 
Illinois (Miller and Tehon 1929; Jones and Fuller 1955); Indiana 
(Deam 1932); Kansas (Hitchcock 1899; Gates 1938; Stephens 
1969); Missouri (Steyermark 1963); Nebraska (Pool 1919); North 
and South Carolina (Radford, Ahles, and Bell 1965, 1968); Ohio 
(Braun 1961); Oklahoma (Williams 1973); and Wisconsin (Fassett 
1930). One recent reference shows dots for counties in 4 States 
(including 2 not named above), North Dakota, South Dakota, 
Nebraska, and Kansas (Stephens 1973). Maps of several species in 
this volume were included in the reference on wild flowers of 
western Pennsylvania and parts of adjacent States by Jennings 
(1953). Besides the 14 States mentioned, 2 
theses not yet published are Virginia (James 1969) and Arkansas 
(Tucker 1976). 
Examples of references with detailed information but no maps are: 
Connecticut (Graves and others 1910); Delaware and Eastern Shore 
of Maryland and Virginia (Tatnall 1935); southern New Jersey 
(Stone 1911); Maine (Hyland and Steinmetz 1944; Ogden, 
Steinmetz, and Hyland 1948); New York (Taylor 1915); Vermont 
(Seymour 1969); and Virginia (Massey 1961). 
“Index Holmensis, a World Index of Plant Distribution Maps” 
(Tralau 1969-74) cites published maps by species and will be 
valuable in future compilation. The first three volumes on gymno- 
others with maps in 
sperms and monocotyledons haye very few species charted here. 
Hardwoods will be 
dicotyledons. 
The ranges of some native tree species of Eastern United States 
continue northward into Canada and have been compiled from 
published references. “‘Native Trees of Canada” (Hosie 1969) 
contains small maps of the forest tree species. Trees of Newfound- 
land and Labrador were charted by Bearnes (1968). Some species of 
Ontario were mapped by Fox and Soper (1952-54) and Soper and 
Heimburger (1961). Two floras of eastern provinces contain dot 
maps, that of Prince Edwards Island by Erskine (1960) and of Nova 
Scotia by Roland and Smith (1969). Many species of Quebec were 
plotted by Rousseau (1974). 
Among the most detailed published maps are those of taxonomic 
monographs and those of a single species based upon extensive field 
work, such as a doctoral thesis. However, few species of this volume 
covered in the remaining volumes on 
have been so thoroughly studied. Kalmia latifolia, mountain-laurel, 
was plotted by Kurmes (1967). Examples of generic monographs 
with maps among the minor eastern hardwoods are: Aesculus 
(Hardin 1957); Amelanchier (Jones 1946); Bumelia (Clark 1942); 
Cercis (Hopkins 1942); Fraxinus (Miller 1955); Osmanthus(Green 
1962); Ptelea (Bailey 1962); Rhamnus (Wolf 1938); Rhus (Barkley 
1937); and Tilia (Jones 1968). 
Also, a few publications about plant families have species maps. 
Two in the legume family, Leguminosae, are “The legumes of 
Texas” (Turner 1959) and Subfamily Mimosoideae (Isely 1973). The 
eyrilla family, Cyrillaceae, was monographed by Thomas (1960). 
The genus Illicium was treated in a larger monograph by Smith 
(1947). The taxonomic review of the tea family, Theaceae, in the 
United States has locality data (Kobuski 1951). 
Examples of generic monographs with distribution data but 
without maps are Bumelia (Cronquist 1945); Cornus (Rickett 1945); 
Erythrina (Krukoff 1939); Forestiera (Johnston 1957); Kalmia 
(Ebinger 1974); Persea (Kopp 1966); Sabal and Serenoa (Bailey 
3 
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