Tiii<; Mt)i\'iiii,v nri.MOTix. 171 



Sinf'P ri/rus calh rijana lins shown \cvy marked rcsistnnfe to peai 

 hlight, and, as it is widely distributed in China, has been found grow- 

 ing on a great diversity of soils, and is extremely vigorous, it may 

 prove very valuable as a stock for our cultivated varieties of pears. 

 Also, since the type found nf Oroville appears to be perfectly at home 

 in the swamps of China, it ought to prove valuable on wet soils, 

 especially on soils along rivers such as those of the great pear region 

 along the Sacramento River, California. This type also appears at 

 home on dry soils. At Oi'oville the trees are growing splendidly on 

 high, dry soil where the drainage is perfect at all seasons of the year. 



The trees at Oroville now belong to Mrs. Leonora Williams, 1334 

 Danielson avenue, through whose courtesy our material of this type 

 was ol)tained. 



The other forms of Pyn(s callcrycnta were obtained through the kind- 

 ness of Dr. C. S. Sargent, Director of the Arnold arboretum, Jamaica 

 Plain, Massachusetts. These forms of this species were collected in 

 central China and introduced into this country in 1908 by ]\Ir. E. H. 

 Wilson of tlie Arnold arboretum. It is of interest to note that Mr. 

 Compere and Mr. Wilson introduced these types of the same species 

 during the same year, although collected in very widely separated 

 localities of China. 



CONCLUSIONS. 



In conclusion I must state that the Southern Oregon Experiment 

 Station has perhaps the largest collecticn of species of Pyrus in the 

 world. In our inoculation experiments most of these have proved 

 quite susceptible to pear blight, while a few have shown marked resist- 

 ance. As I have already called attention to these species in another 

 report,* it is not necessary to discuss them here. I wi-ih to state, how- 

 ever, that we have not found a single species up to the present time, 

 even of the most blight resistant, which is absolutely immune to the 

 disease. In all cases we have been able to produce the disease in the 

 young, vigorous, growing shoots. However, we have at least three 

 species in which we have never l)een able to produce the disease in wood 

 more than one year old. It should also be noted that all of the resistant 

 species found up to the present time have come from China, except one 

 from northern India. 



It is probable that for very cold regions some of the blight resistant 

 forms of the Chinase sand pear, such as the Japan pear seedlings, and 

 others of this type, will prove most desirable as stocks. For the 

 warmer regions Pj/nis calh rijana and its various sub-types appear very 

 promising and should be thoroughly tested. 



Throughout this article the term pear blight has been used to desig- 

 nate the disease commoidy known to American horticulturists as pear 

 blight and seienlificaljy known as Bacillus amylovorus (Bur.) De Toni. 



♦Proceedings of tlio .Ann^rican Pomological Society, Tliirty-fourtli Biennial Session. 



