166 FUNGOID PESTS OF CULTIVATED PLANTS. 



resemble other cankers, and appear to be the result of local irritation. 

 The bark around, which was at first, perhaps, a wound, swells, becomes 

 corky, and of a rusty-brown, covering a patch an inch or more long. 

 When the centre of the tumour is bare, the woody tissue is seen to be 

 dead, and occupied by black dots, which are the thin receptacles of an 

 immersed Phoma, with minute narrowly elliptical conidia (7 x 2 /x,). 

 This is not the cause of canker, but a sequence. Sometimes several scars 

 are confluent at the bottom of stems, and are swollen in a gouty manner 

 by the corky transmutation of the surrounding cell. 



HOYA LEAF- SPOT. 

 Phyllosticta Bolleana (Sacc.), PL XIV. fig. 19. 



Forming spots on the living leaves of Hoya carnosa, which are 

 bleached to a greyish -white, with an irregular brown margin, forming a 

 striking contrast to the bright green of the leaf. The receptacles are 

 scattered over the spot like minute black dots to the naked eye, containing 

 the small elliptical sporules, which are just tinged with grey (4-5 x 



It is doubtful whether the minute fungi of this genus, which forms 

 spots *on living leaves, are to any considerable extent injurious to the 

 plant. They may become so by disfiguring the foliage, especially if they 

 spread themselves, but they are certainly incapable of inflicting such 

 injury as that caused by the various kinds of Anthracnose. Their life- 

 history is at present much involved in mystery. 



Probably, should any of them prove troublesome, it would be well to 

 submit the plants to treatment with one of the copper solutions. 



Sacc. Syll. iii. 70 ; Grevillea, xiv. 39. 



Another leaf -spot (Septoria Hoya) forms various white spots on Hoya- 

 leaves, girt by a brownish ring, sporules threadlike (20-25 x I-!T> /x) or a 

 little club-shaped. In botanic gardens in Italy. 



HOYA ANTHRACNOSE. 

 Glceosporium affine (Sacc.), PI. XIV. fig. 18. 



This spot has recently made its appearance in hot-houses at Glasgow, 

 and may soon travel southwards. It was previously known in Italy ; 

 it belongs to a genus which is eminently destructive, and includes many 

 pests. 



The spots on the leaves are variable, both as to size and form, becom- 

 ing bleached or whitened, having little pustules on the surface. These 

 pustules are scattered, and consist of small discoloured cells, without 

 any true or distinct outer covering or receptacle, nestling beneath the 

 blackened cuticle. The pustules appear chiefly on the upper surface. 

 At length an irregular opening is made, and the conidia ooze out in the 

 form of a tendril. They are cylindrically oblong, rounded at the ends, 

 colourless, and spring at first from the cushion-like base of the pustule, 

 borne on short delicate basidia. Conidia of moderate size for the genus 

 (14-20 x 4-6 /u). 



