FUNGOID PESTS OF CULTIVATED PLANTS. 69 



pustules soon appear, at first covered by the cuticle. The paleness is 

 caused by the internal mycelium which pervades the tissues. 



The pustules are small and numerous, generally arranged upon the 

 spots in concentric rings, or parts of rings, with a tendency to coalesce. 

 The spores are soon exposed by rupture of the cuticle, when they are 

 powdery and of a chestnut-brown colour. 



The uredospores are at present unknown. 



The teleutospores are subglobose, or rather pear-shaped (19-30 x 

 14-24 JLI), and sometimes irregular by compression, quite smooth, and of 

 a pale brown. The epispore, or spore coating, is of equal thickness 

 throughout, and not thickened at the apex, as in many other species. 

 There is a short hyaline stem, which soon disappears. 



Its area of distribution, outside this country, includes France, Germany, 

 Austria, Hungary, Greece, Italy, Egypt, and South Africa. 



It is possible that spraying with one of the fungicides may be of a 

 little service, but the perfection and dispersion of the spores should be 

 prevented by picking and destroying infected leaves. 



Sacc. Syll. vii. 2014; Cooke M.F. 213; Cooke Hdbk. No. 1548; 

 Plowr. Brit. Ured. 141 ; Grevillea, vii. 138. 



BLACK SMUT. 

 Sclerotinia bulborum (Wakk.), PI. IX. fig. 135. 



A pest under the name of "black smut" has appeared around 

 Haarlem, where it has been very destructive to Hyacinth culture. It is 

 not a " smut " according to our acceptation of the term, but a Sclerotium. 



It makes its appearance after flowering, causing the leaves to turn 

 yellow and fall off. No external mycelium is to be observed, except at 

 the base of the leaves. The bulb is completely permeated with mycelium, 

 and black irregular nodules appear on the surface, mixed with some that 

 are softer and paler coloured. These are the " sclerotia," or nodules of 

 compact mycelium. These nodules are like resting scores, and must pass 

 through a period of quiescence, so that they will not germinate until the 

 following spring. 



If the bulbs are potted, and watered copiously, at the period when 

 their activity should commence the sclerotia will germinate and produce 

 the little Peziza cups, resembling those produced from the sclerotium of 

 the Potato. To this Peziza-form Wakker has given the name of 

 Sclerotinia bulborum. The sporidia are binucleate (16 x 8 /z). 



There is one peculiarity about these sclerotia, that when cultivated in 

 a nutrient solution they will form a mycelium and produce secondary 

 sclerotia. 



It is needless to say that when once a bulb is attacked remedy is 

 hopeless. Onion bulbs are also liable to attack. 



Gard. Chron. May 12, 1894, p. 592 ; Mass. PL Dis. 380. 



HYACINTH YELLOW DISEASE. 

 Pseudomonas Hyacinthi. 



A disease affecting Hyacinth bulbs has been described under the name 

 of " yellow disease " which appears on them in the autumn, filling the 



