Brown: THE GENUS CRATAEGUS 257 
possession of neglected pastures, fence-rows, and untilled ledges ; 
(c) the older botanists had no time for the intensive study of a 
genus of numerous closely allied forms, such as Crataegus. 
2. Many or most of ‘the large number of species now being 
described,” if proper species at all, would have to rank as “ ele- 
mentary species.” But some recently made species are, I believe, 
mere “ fluctuations”’ or ‘ forms.” 
3. I have never raised seedlings of Crataegus ; Dr. Sargent has 
in large quantities, and he insists on it that as respects foliage they 
breed true to seed. 
4. I must confess I have never attempted to hybridize Cra- 
taegus species ; I know of no one who has attempted it with our 
American species. The few species of Europe cross in many ways 
(see Focke’s Pflanzen-mischlinge, p. 146). I know of several 
cases of what appear to be natural hybrids, ‘local species,’’ each 
quite intermediate between the two supposed parent species with 
which it is associated. The Rosaceae are of all orders most pre- 
disposed to hybridize. Rosa, Rubus, Geum, Amelanchier, and 
Malus are notorious for the forms resulting from interbreeding. 
By analogy we should expect the same condition of things in 
Crataegus. The array of closely allied forms (hardly distinguish- 
able even by an expert) present a condition of things in Crataegus 
that is perfectly paralleled in Rudus, Rosa,and Viola. The multi- 
plicity of even stable forms that may result (in the working out 
of Mendel’s Laws) from one pair of parents is astonishing. The 
swarms of ‘elementary species,” I suspect, have in some instances 
come about in this way. 
5. There may be “ mutations” in Crataegus ; but it would be 
very hard to prove. 
John Dunbar, of the Park Department, Rochester, N. Y., is 
another enthusiastic student of the genus. In answering the ques- 
tions, he says: 
1. No doubt they (the early systematists) believed honestly, 
without thorough investigation, that the large number of variations, 
which, of course, they could not help but detect, were mere forms 
of several species. 
2. They are true species. 
