168 



THE MONTHLY BULLETIN. 



Pynis calleryana iisiially has throe or four pistils, rarely two or 

 five. Pyrus sinensis iisuall}- eoutains five pistils, rarely three or four. 



The difference between the leaves of the two species, especially the 

 form and the nature of the leaf margins, is so noticeable that two species 



Fig. 59. — Leaves of two specie.s of Pyrus. The long slender leaf with sharp 

 serrations is Pyrus sinensis. The other two are types of Pyrus calleryana. 

 The one in the center is from a tree at Oroville, Cal. About one-lialf natural 

 size. (Original.) 



never need be confused. Even in the nursery row any nurseryman 

 can readily distinguish them. 



BLIGHT RESISTANCE. 



Mr. Compere in his article called attention to the fact that the trees 

 at Oroville had never shown any signs of blight. During the past 

 winter the writer carried on inoculation experiments on three-year old 

 trees of the type from Oroville and other forms of Pyrus calleryana 

 in the greenhouse. These inoculations have shown that this species, 

 while not absolutely immune to pear blight, is very resistant to this 

 disease. While the disease developed in the one-year old branches, it 

 would never progress into the two and three-year old wood. Inocula- 

 tions made on the tips of vigorous growing shoots produced the disease 

 readily, and on several branches it extended down these young slender 

 shoots for a distance of from two to three feet. As soon as the disease 

 reached the older, harder wood it would stop. In no case did it develop 

 in branches more than one-half inch in diarr.eter. The three-year old 

 trunk of one tree of the Oroville type has been thoroughly inoculated 

 at various times without producing the disease. For example, the 



