85 



requires heavier feeding. At any rate the thickened, infected 

 leaf areas lose their chlorophyll and the sugar-forming power 

 of the tree must be much reduced. Our infected Bechtal crab 

 shows poor health by its lessened flowering and its winter-killed 

 branches. The apple rust lives for only one season but it is apt 

 to recur annually in this region of abundant cedars. Their 

 abundance makes the exterminatior\ of the cedar link impracti- 

 cable; the apple growers instead must hunt for immune varieties 

 of apple or keep busy with sprays. (20) 



Red cedar is host to some twelve different species of the 

 rust, Gymnosporangium. (9) Four of these occur in New Eng- 

 land and I am chagrined to have found only two in Norton. 

 The bird's-nest rust, Gym7wsporangmm nidus-avis, causes more 

 disturbance to its host than does the cedar-apple rust, Gymno- 

 sporangium juniperi-virginianae. Not only do the leaves of 

 infected branches develop the needle-shaped form characteristic 

 of a seedling tree, an effect caused also by the apple-cedar rust, 

 but the growth of the main axis is checked and the branches 

 grow in a dense cluster: the "bird's-nest." (58) Red cedar is 

 hardy stock. I have found it holding its ow^n against these two 

 parasites . . . with gay "cedar apples" on its green branches 

 while half-dead "bird's-nest" clusters distort other branches. 

 On these latter, gelatinous masses of teleutospores ooze out, 

 in the spring, from cracks in the bark. 



Around Norton shad bush is the most frequent alternate 

 host for the bird's-nest rust. Both leaves and fruit show annually 

 a heavy eruption of spermatia and aecidiospores. Shad bush is 

 also alternate host to another Gymnosporangium of the Norton 

 group: Gymnosporangium clavariaeforme which infects the 

 prickly dwarf cedar or juniper. (58) Plants which w^ere moved 

 from the fields to the campus rock-garden develop each spring 

 the characteristic masses of yellow^ teleutospores along the 

 branches. Again the pathologist downs the gardener and keeps 

 the rather scraggy juniper as a prized exhibit. 



This is, indeed, a small list of Gymnosporangiums for Nor- 

 ton. I reflect regretfully upon time spent in the laboratory 

 instead of in the field. We have white cedar as w^ell as red cedar, 

 and sweetfern in abundance but I have never found the \vhite 

 cedar rust which, unlike its thirty sister species, chooses sweet- 

 fern for its alternate host instead of one of the apple tribe. (34) 



