WHITE-PIXE BLISTER RUST. 53 



Grossularioides. — Ribes lacustre: Dead spots formed early on infected leaves; 



sori sparse or diffuse, irregular spots: telia rather scattered. 

 Grossularia. — Rihes lobhii: Sori thickly crowded on rounded spots, telia well de- 

 veloped. 



Ribes menziesii: Sori sparse on small irregular spots. 



Ribes spedosum: Sori seated closely together on large rounded spots, telia 



rather short. 

 EuGROssuLARiA. — Ribes alpestre: Sori thickly crowded on large rounded spots, 

 telia short. 



Ribes curvatum: Sori crowded on rounded spots on young leaves, on irregular 

 spots on old leaves; telia quite plentiful; spots with reddened edges late in 

 season. 



Ribes cynosbaii: Sori plentiful on definite spots, which are usually rounded 

 (PI. V, fig. 1); spots sometimes wedge shaped, lying between two branching 

 veins of the leaf; telia crowded in small groups, 1 to 1.^ mm. long, rarely over 

 entire leaf surface. 



Ribes divaricatum: Soil scattered on rounded spots. 



Ribes missoiiriense: Sori crowded on rounded indefinite spots on youns leaves, 

 densely crowded on small leaves, dead irregular spots on old leaves. 



Ribes lepianihum: Sori very scant; dead spots appear so early that uredinia 

 can form with difficulty, often only one uredinium on a spot, many spots \vith- 

 out sori; produces the least sori of any species yet noted. 



Ribes hirtellum: Sori usually crowded thickly on small spots; uredinia on 

 small rounded spots; telia small, crowded densely; on older leaves, on small 

 indefinite, irregular spots bounded. by veinlets; spots sometimes purplish on 

 the edges. 



Ribes oxyacanthoides: Like R. hirtelluin. 



Ribes rcclinainm: Sori rather sparse, on small irregular spots of dead tissue. 

 There is a tendency toward a reddening or purpling of the edges of the spots 

 on old leaves. (PI. V, fig. 3.) 



Ribes rotundifolium: Sori crowded on small irregular spots. The spots die 

 early and are likely to become reddish around the edges even on rather young 

 leaves. It is rather rare for the entire leaf to become covered with sori. 



Ribes setosum: Much like R. cynosbaii. 

 Hemibotrya. — Ribes fasciculatum vars. chinense and japonicuvx: Sori densely 



crowded on large rounded spots. 

 Diacantha. — Rihcs diacaniha: Sori on rounded spots. 



Ribes giraldii: Sori scattered on rounded spots. 



In general, it may be said that R. nigrum and its varieties is the 

 optimum host species among the Ribes for Cronartium rihicola. 

 Rihes aureum and R. odoratum and their varieties are perhaps next 

 to R. nigrum in favoring the growth of the fungus. R. redinatum 

 does not take the disease readily, but is by no means immune to it. 

 In fact, no species or variety yet fully tested is entirely immune. 

 R. leptanthum probably produces fewer sori for the extent of infection 

 than any other species. This is caused by tHie very early death of 

 the infected tissue. 



PALE COLOR OP INFECTED SPOTS ON THE LOWER SURFACE OF RIBES LEAVES. 



The production of sori on an infected spot on the lower surface of 

 Ribes leaves is often preceded for one, two, or three days by a pale 



