FUNGOID PESTS OF CULTIVATED PLANTS. 75 



This species is known in France, the Ardennes, Germany, Switzer- 

 land, Italy, and Siberia. 



No associated cluster-cups are known. 



Sacc. Syll. vii. 2284 ; Cooke M.F, p. 203 ; Hdbk. No. 1466 ; Plowr. 

 Brit. Ured. 190. 



Cluster-cups (JEcidium Iridis) are known in North America on leaves 

 of Iris versicolor. 



IRIS LEAF-BLOTCH. 

 Heterosporium gracile (Wallr.), PI. V. fig. 90. 



One of the most persistent and troublesome of Iris diseases is this 

 mould, which appears at some seasons with astonishing vigour upon the 

 leaves of Iris germanica and other species. 



The upper portion of the leaves turns brown and decays or rots, and 

 some plants are soon killed ; large dark spots, becoming black, rounded, or 

 elliptical, from half to one inch in length, with a brown border, appear 

 on the brown parts, or on the still green leaves, velvety with the parasitic 

 mould. In other cases the spots are smaller and more numerous, with a 

 narrow brown margin, and simply bleached or dead tissue, on which are 

 sprinkled a few tufts of the mould. 



The mould consists of rather short and thick jointed threads in small 

 tufts, and of a sooty-brown colour, bearing singly, or nearly always, the 

 conidia of variable size, some of which are elliptical and without division, 

 whilst others are elongated, and once or twice divided transversely into 

 cells (35-70 x 14-20 /u), and also of a smoky colour, the surface rough 

 with minute points. 



This disease seems to be known in France, Germany, Italy, the Cape 

 of Good Hope, New Zealand, and North America. 



If not too firmly established, syringing with one of the copper solu- 

 tions may be of some service ; but the conidia germinate freely at every 

 joint, and if not destroyed will quickly spread the disease. 



Gard. Chron. June 9, 1894, p. 718 ; Sacc. Syll. iv. 2308 ; Journ. 

 R.H.S. xxvi. 1901, p. 450. Reported also on Narcissus, Journ. R.H.S. 

 xxviii. 1904, p. 679. 



IRIS BULB SCAB. 

 Mystrosporium adustum (Mass.), PL V. fig. 92. 



Bulbs of Iris reticulata have lately been affected and frequently 

 destroyed by the incursions of a black mould, previously unknown, and 

 which forms black crust-like patches on the outer sheath, gradually 

 speading to every part. 



There is a profuse dark mycelium, from which arise the short branches 

 bearing the large and much-divided conidia. These latter are elliptic- 

 oblong or ovate, with obtuse ends, and from five to seven transverse 

 septa or divisions, which are again subdivided by longitudinal septa in a. 

 muriform manner. The divisions are often oblique, and sometimes with- 

 out longitudinal divisions (45-60 x 20-22 p), smooth, dark brown, and 

 semi-translucent, produced at the tips of the threads, or at the ends of 

 short branches. 



