98 DISEASES OF CROPS. 



From the author's researches, compounds of iron appear 

 to he detrimental to the growth of most parasitic fungi ; 

 and the absence of soluble, or readily assimilable iron 

 compounds in a soil, may produce sickly plants liable to 

 fall an easy prey to the attacks of parasitic fungi. Tig. 

 38 A illustrates a panicle of grass infested with Isaria 

 fuciformis, whose mycelium grows on all parts of the 

 host-plant, especially the leaves and stems, which it often 

 binds together. The fungus is chromogenic {i.e., produces 

 colour) — the colour of the mycelium being from pink to 

 red — and consists of a compact mass of cells which fre- 

 quently sends out aSrial tufts (Fig. 38 a). The cells at 

 the extreme ends of these tufts divide and give rise to 

 numberless conidia (Fig. 39 B). These conidia, or spores, 

 germinate on grasses, and again reproduce the mycelium 

 of I. fuciformis. The fungus tufts are easily detached, 

 and if they fall upon a suitable medium for development 

 they reproduce the mycelium of the fungus. Very little 

 (beyond what has already been stated) is known of this 

 fungus or its habits. " It is quite possible that I. fuci- 

 formis may be an early condition of a Torrubia belonging 

 to an insect or plant host." Certain species of Torrubia 

 infest truffles, mosses, and insects. It has been stated 

 that grass infested with I. fuciformis produces a diseased 

 state of the lungs when farm animals are fed upon it ; but 

 this statement requires confirmation. 



Prevention. — (1) The drainage of all grass lands, es- 

 pecially those in the South and South-west of England, 

 has a tendency to lessen the attacks of this fungoid pest. 

 (2) As I. fuciformis only makes its appearance from Sep- 

 tember to the following January, it would be well for 

 farmers to remove the grass before the appearance of the 

 fungus. 



