466 DISEASES OF CULTIVATED PLANTS 



conidia produced in simple or branched chains, globose or 

 elliptical, continuous, coloured. 



This genus is in reality only a condition of Cladosporium 

 epiphyllum, and is figured as springing from broken conidio- 

 phores of Cladosporium epiphyllum on p. 472, Fig. 141, of this 

 book. C. epiphyllum, again, is only a conidial form of 

 Sphaerella tulasnei (Janczewski). Finally, the Hormodendron 

 condition is the well-known Dematium puttulans of De Bary. 



Barley leaf blotch (Hormodendron hordei, Bruhne) is the 

 cause of spots and perforations in the leaves of barley, and 

 when present in quantity on both leaves and haulms, stunts 

 the plant and causes a poor yield. It is perhaps the most 

 omnivorous of fungus parasites known. I have found it on 

 many wild and cultivated plants, as hollyhock, cabbages, 

 deadly nightshade, enchanter's nightshade, Catalpa big- 

 nonioides, etc. etc. It appears under the form of pale green, 

 translucent spots on the leaves, which finally become per- 

 forations, and increase in size, often to a considerable extent, 

 and give the impression of having been eaten by a slug or 

 snail. It is scarcely too much to state that 90 per cent. 

 of the perforations with ragged outlines, so frequently met 

 with on otherwise vigorous foliage, are caused by this fungus. 

 If a perforated leaf is placed on damp blotting-paper in a 

 Petri dish, in the course of a day or two numerous fruiting 

 branches of the Hormodendron will be found projecting from 

 the edges of the wounds, when examined under a low power 

 of the microscope. 



The spores of Cladosporium herbarum^ on germination, as 

 also the broken and old conidiophores of the same fungus, 

 produce the Hormodendron when in contact with moisture. 

 The Hormodendron conidia infect living plants, and continue 

 to reproduce the Hormodendron form throughout the summer 

 season, causing a continuation of the epidemic, which, when 

 favoured by congenial surroundings, as when the host is a 

 cultivated plant grown in houses, often assumes serious pro- 

 portions, as in the case of cucumber leaf blotch, which I find 

 to be far more frequently due to Hormodendron hordei than 

 to Cercospora melonis (Cooke). 



As will be gathered from what has been stated above, the 

 cause of all this mischief is only an intermediate condition of 

 some higher form of fungus. The only certainty respecting 

 its origin is that it originates as a Hormodendron from the 



