( 4 2I) 



of seed being entirely prevented. It is interesting to note that 

 these affected berries show the same abnormal tendency to hang 

 on as do fruit-mummies caused by the attacks of other fungi. 

 On larger fruits such as apples, pears, and quinces the infected 

 area is often only a portion of the surface but the fruit is always 

 dwarfed and often distorted. 



The leaf-inhabiting forms, aside from the injury caused by the 

 arrest and utilization of food-materials, may work a still greater 

 injury to the health of the host by bringing about a premature de- 

 foliation. In severe infections of apple trees it sometimes happens 

 that the leaves fall before the aecia have time to mature. Heald 

 (1909) reports that in severe cases an ordinary apple leaf may have 

 as many as 200-300 separate points of infection. 



Economic Importance 

 The importance of the members of the apple and cedar families 

 is so great economically that any factors causing disturbances in 

 their health are worthy of consideration. Orchardists have been 

 aware for some time that certain species of rust (Gymnosporan- 

 gium) often attack the stable orchard crops, such as apples, pears, 

 and quinces, in a very virulent and destructive manner. It is 

 not so well appreciated that many of the wild and native species 

 of the apple family which are being used for decorative puposes 

 are also susceptible to rust-diseases, especially when planted in 

 proximity to members of the cedar family. The importance of 

 these rusts from the standpoint of the cedars has, perhaps, been 

 still less appreciated, at any rate it has been much less emphasized. 

 Heald (1907), however, writes "those who have cedars — and there 

 are many in this section [Nebraska] who value them as much as 

 they do their apple trees — have been clamoring for assistance 

 in saving them from the inroads of this fungus [G. Juniperi- 



rchard crops there are only a 



importance. G. Juniperi-virginianae (G. 



macropus) is the "orchard 



rust" of American horticultural writei 



•s and is the commonest 



species occurring on apple in this count! 



ry. It attacks the leaves 



chiefly but not infrequently the young fr 



uits also become infected. 



The common aecial hosts of this species 



are the wild crab-apples, 



and it is interesting to note in this com 



lection that although the 



