102 



HEART-ROT 



made very nearly up to the margin, so that in the resting 

 stage the fungus has the appearance shown in fig. 39. 



A very constant feature of the fructifications of this 

 species is the holes in the sporophores. When the latter 

 encounter a small root or stick, or even a blade of grass, 

 they grow round it, leaving a hole such as those seen in 

 fig. 39. These holes differ from those made under similar 

 circumstances by most other fungi, by being surrounded by 



a reddish -brown ridge of sterile 

 tissue. This ridge forms one 

 of the most useful features for 

 identification. Fig. 39 shows 

 the appearance of the lower 

 surface of the pores. It will 

 be seen that they vary from 

 circular to irregularly oval or 

 elliptical. Their width is 

 usually about 0-25 mm. 

 ( = TOO in.), but may be any- 

 thing from 0*15 to 0-6 mm. 



The pores are not fertile 

 through their whole length at 

 the same time. As a fructi- 

 fication grows older the upper 

 part of each pore becomes 

 filled with hyphae, and only 

 the lowermost 1 to 2 cm., i. e. the part nearest the openings, 

 bears spores. During the summer the pores lengthen and 

 the fertile zone moves downwards. Fig. 38 shows the pores 

 in longitudinal section ; two pieces of the fungus are here 

 cut through, in each of which two years' growth can be 

 distinguished. 



In the fertile region each pore is lined with the hymonium , 

 a layer made up of basidia and paraphyses. Fig. 41, A, 

 shows this layer as seen in a longitudinal .section of the 

 pores. The basidia are 30-40/x long and 8-10 p broad. 

 Normally each bears four spores (ft.), but basidia with two 

 spores are frequent (a.), and basidia with three or five spores 



FIG. 41. Pomes annosus : A, 

 hymenial layer inside a pore ; a., a 

 young basidium with two spores ; 

 b., older basidium with four spores ; 

 p., paraphysis ( x 200) ; B, single 

 spore showing attachment to basi- 

 dium ; &., basidium ; st., sterigma ; 

 se., septum ; sp., basidiospore ( x 

 1000) ; c, ripe spores after shedding. 



