390 DISEASES F CULTIVATED PLA] 



year changes to a peculiar greyish-yellow tint, so that in a 

 longitudinal section the wood presents a series of alternating 

 stripes of colour, the larger medullar}- rays retaining the brown 

 tint Ion.- -: The fruit of the fungus eventually appears on 

 wounded branches, or comes to the surface of the trunk in 

 places where the bark is destroyed. 



The form of the sporophore varies much, depending on 

 the conditions under which it is developed. Wnen growing 

 on a large surface, as a trunk it often extends for a consider- 

 able distance without forming a true pileus, but remains as an 

 -ular, flattened patch. When growing on a branch it is 

 often more or less knobbed or lobed, sometimes with an 

 attempt at a stalk, whitish or tinged yellow, 2-3 in. across, 

 upper surface with irregularly notched teeth or spines, edge 

 with club-shaped, sterile teeth, under surface with pointed 

 spines 3-6 in. long. 



Hartig. Die Z sch. dcs Holzes, p. 97. pi. xi. 



Prillier. '.' t/es Agric. 1, p. 321 (lb 



THELEPHORACEAE 



flexed or entirely 

 adnate to the -atum ; hymenium even, smooth, and 



polished, or with projectin. ..iia : spores hyaline 



iured. 



HYPOCHNUi 



Mycelium forming weft sp- 



ot' the substratum. dia constantly 



d tufts over I -ace of the 



urn. 



elium, . 

 in the basidi;. spores at the .. 



g a co- hymenium. 



ng of c iia. 



Potato collar fungus I // . . Prill, an I 



forms a greyish, or fawn-coloured film round the 



living haulms of potatoes. This film begins at the ; 

 where the haulm en rg from the ground, and extends 

 ;rds for three or four inches. It consists of a lot 



