312 DISEASES OF CULTIVATED PLANTS 



'Carnation rust' are suitable here. Portions of diseased 

 plants should not be used for propagation, even although 

 they do not show the disease. 



Saxifrage rust (Puccinta pazschkei, Dietel) once severely 

 injured the foliage of a batch of Saxifraga longifolia in Kew 

 Gardens, some of the plants being killed outright. Other 

 species of Saxifrage are attacked on the Continent, and 

 probably the fungus was introduced into this country along 

 with living plants. 



Teleutospore sori usually grouped in concentric circles on 

 the upper surface of the leaf, dark brown. Teleutospores 

 elliptic-oblong, rounded at both ends, slightly constricted at 

 the septum, distinctly warted, pale brown, 30-45x15-20 /A, 

 pedicel hyaline, slender. 



Puccinia saxifragae (Schl.), parasitic on our wild Saxifrages, 

 is distinguished from the above in having the wall of the 

 teleutospore delicately striated instead of warted, and in 

 having a pale apical papilla. 



PHRAGMIDIUM (LINK.) 



Spermogonia flattened, orbicular ; aecidia ( Caeoma) in 

 roundish clusters, confluent, and broadly effused, aecidio- 

 spores in chains ; uredospores formed singly at the tips of 

 hyphae ; teleutospores transversely 3-many-septate, upper cell 

 with i germ-pore, remainder with 4 germ-pores. 



Rose rust (Phragmidium subcorticatum. Winter) is a very 

 troublesome pest to the rosarian, attacking more especially 

 hardy hybrid varieties. It is also common on wild roses. 

 All three forms of the fungus grow on the same host. The 

 aecidium appears first under the form of deep orange, 

 powdery patches on the leaves and young shoots, often 

 causing distortion of the parts affected. At a later stage the 

 patches become deeper orange, owing to the formation of 

 uredospores. Lastly, the teleutospores form minute black 

 dots on the under surface of the leaves. 



Aecidiospores orange, aculeolate, 17-28 X 12-20 p. 



Uredospores variable in form, 17-32 X 12-24 /*, delicately 

 aculeolate. 



Teleutospores oblong, obtuse, with a white apiculus, warted> 



