Brown: THE GENUS CRATAEGUS 253 
Many parts of the country have not yet been worked over 
thoroughly, and new descriptions are bound to appear for some time 
to come. 
Species do not seem to be so abundant in western North America 
or in other parts of the world. Howell’s Flora of Northwest 
America includes but two species ; Jepson’s Flora of Western Mid- 
dle California, one; Rydberg’s Flora of Colorado, but five; and 
the Coulter-Nelson New Manual of Botany of the Central Rocky 
Mountains, nine. There are about twelve species from the Rocky 
Mountains west, north of Mexico. Grisebach lists none in the 
Flora of the British West Indian Islands. In Bentham and 
Hooker’s Genera Plantarum, but twelve species are said to be 
found in Europe, Asia, and Japan. Itremains to be seen whether 
or not many more species will be found in these regions upon 
closer study. 
A consideration of the foregoing facts brings up a number of in- 
teresting questions. Why did not the systematists discover the 
great number of species years ago? We cannot say they did not 
do careful work. Can it be that the number of species has multi- 
plied greatly within the last few decades? Have the older species 
been hybridizing so that many of the formsat present are hybrids ? 
In order to get some light on some of these questions the fol- 
lowing list of questions was sent to each of the following men, 
who are regarded as leading students of the genus in this country: 
C. S. Sargent, W. W. Eggleston, W. W. Ashe, C. D. Beadle, 
Ezra Brainerd, and John Dunbar. 
1. Why did not the sytematic botanists discover the large 
number of species of Crataegus years ago? 
2. Do you consider the species now being described elemen- 
tary species ? 
3. Do the species breed true or come true to seed? 
4. Will different species hybridize ? 
5. Do you consider the numerous species to have arisen as 
mutations ? 
Professor Sargent, director of the Arnold Arboretum, has 
perhaps devoted more time to the study of the genus than has 
any other man and has described many new species. In answer 
to the questions, he says: 
