PLANTS OF NORTH ELBA 87 



ROSACEAE 



Prunus Pennsylvanica L.f. 



Wild red cherry. Pin cherry 



Along fences and in recent clearings and wind slashes. Common. 

 May and June. 



This is a small tree of rapid growth and short life. It springs up 

 abundantly wherever clearings have been made in the forest. Its fruit 

 is smaller than the fruit of our other native species and is quite acid. Its 

 branches are often disfigured by oblong irregular black swellings com- 

 monly called black knot. These knots are caused by a parasitic fungus, 

 Ploivrightia jnorbosa (Schw.) Sacc, whose spores, lodging on the 

 branches, germinate, under favorable conditions, and entering the newly 

 formed tissue 'by means of their germinal tubes cause an unnatural en- 

 largement of the affected part of the branch. The bark ruptures and 

 the exposed tissue is soon covered by an olive green mold which in turn 

 is replaced by a multitude of small crowded black globular bodies, the 

 spore cases of the fungus. The spores escaping from these are liable to 

 lodge on and produce the disease in any cultivated cherry or plum trees 

 that may be growing in the vicinity, and thereby injure the fruiting 

 capacity of these trees. 



Prunus Virginiana L. 



Choke cherry 



Roadsides, clearings and along fences. Very common. June. 



The choke cherry fruits abundantly but its fruit has an astringent 

 quality that interferes with its usefulness. If this could be overcome it 

 would be a valuable addition to our supply of hardy fruits. It is a shrub 

 or sometimes a small tree and grows freely in all parts of the Adiron- 

 dacks where clearings have been made. A dwarf form occurs in which 

 the flowers are very small and the racemes are only an inch or an inch 

 and a half long. 



Prunus serotina Ehrh. 

 Black cherry. Wild black cherry. Rum cherry 



Trees of this species are scattered over nearly the whole town, growing 

 both in the woods and in cleared lands. In the woods it makes a tall 

 tree with a trunk suitable for lumber when sufficiently straight. It 

 flowers in June. 



