140 FUNGOID PESTS OF CULTIVATED PLANTS. 



HAZEL-LEAF MILDEW. 

 Phyllactinia suffulta (Sacc.). 



Filberts being cultivated to a considerable extent as a table fruit, the 

 shrub will fall more naturally into position here than in the shrubbery. 

 The name by which the mildew was known for very many years was 

 Phyllactinia guttata, but it has since suffered in the lust for change. 



The under surface of the leaves is frequently covered with a delicate 

 white mildew consisting of a creeping interwoven mycelium of .thin 

 threads with short erect branches bearing conidia. In the course of 

 time the little dark globose receptacles make their appearance, scattered 

 over the surface of the mildew. These little conceptacles are encircled 

 by a ring of spine-like, pointed, divergent appendages with a swollen base, 

 which stand around and guard the receptacles. 



Each receptacle encloses from four to twenty hyaline pouches, or asci, 

 which contain the sporidia, of which there are usually two, sometimes 

 three or four in each ascus (40-50 x 22-25 /*). 



This is one of the superficial fungi to which it is believed that the 

 application of sulphur is beneficial, as in the case of the Hop mildew. 



Sacc. Syll. i. No. 13 ; Mass. PL Dis. 98, 361, fig. 16 ; Cooke M. F. xi. 

 figs. 219, 220; Cooke Hdbk. No. 1912 ; Tubeuf, Dis. 179, fig. 



HAZEL-LEAF SPOT. 

 Septoria Avellana (B. & Br.). 



This leaf-spot was recorded by Berkeley, but does not appear to be of 

 very common occurrence. The receptacles are found on the under 

 surface of the dry and bleached parts of the leaves, but the sporules are 

 rather anomalous in size and form for this kind of spot, since they are 

 fusiform and curved (10 /* long). 



The species has also been observed in Italy. 



Grevillea, v. p. 56 ; Sacc. Syll. iii. 2717. 



HAZEL-LEAF BLOTCH. 



Gnomoniella Coryli (Batsch). 



This fungus has long been known on Hazel leaves, and has had its 

 name changed a great many times. It occurs on the living leaves in 

 black shining raised patches on the under surface, resembling little drops 

 of pitch. Each cluster is composed of several receptacles arranged in a 

 circle and immersed in the black stroma, with long projecting necks, 

 each neck surrounded by a white fringe-like collar. 



Within the receptacles are a series of cylindrical tubes, or asci, which 

 enclose the sporidia, eight of which are contained in each tube, and each 

 one is colourless and oval, without any division (7x3 /u). 



When these leaves fall to the ground the sporidia soon arrive at 

 maturity, and are discharged to fulfil their duty in the perpetuation of 

 the species. 



There is an earlier and imperfect stage (Leptothyrium Coryli), in 



