348 



Report of the Horticulturist of thb 



on apple, pear, and quince fruits when inoculated with cultures of 

 Sphaeropsis from the different hosts. 



Table I. — Spore Measurements of SniiEROPSES from Different Sources 



AND ON Different Hosts. 



Hosts from which cultures of Sphasropsis 

 \vere obtained . 



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Pear tree tmgs 22 30 



Quince tree limbs 23 29 



Apple tree limbs 26 29 



Japanese plum, Prunus triflora, Roxb. 28 30 



Hawthorn, Cratfeorus oxyacantha, L. . 21 28 



Porsimmon, Diospyros virginiana, L. . 21 28 



Wild crab, Pyrus coronaria, L 21 28 



Sumach, Rhus typhina, L 23 29 



Bitter sweet, Celastrus scandens, L. . 22 



Apricot, Prunus armeniaca, L 22 30 



Choke cherry, Prunus vir^iniana, L.. 21 29 

 Hop horn beam, Ostrya virginica, 



Willd., decorticated wood 22 28 



Mulberry, Morus alba, L 21 



European plum, Prunus domestica, L. 21 25 



Elder. Sambucus canadensis, L 21 29 



Pear leaves 24 30 



29 

 29 

 30 

 30 



28 

 27 

 28 

 30 



The table is of interest in that it shows that the average size of 

 spores of Sphaeropsis varies according to the host on which they 

 are grown. For instance the pycnidia and spores as they grow 

 on pear wood are somewhat smaller than those that are found on 

 apple wood, yet the spores produced on apple fruits inoculated 

 with cultures from either host, are of the same size and character ; 

 similarly, though not shown in the table, when pear trees 

 are inoculated with cultures of Sphaeropsis taken from apple trees 

 the resulting pycnidia and spores are of the average size of those 

 found in nature on pear tree bark. 



The spore measurements also show that in most cases there is 

 but little difference in the average size of the spores of Sphaeropses 



