128 HEART-ROT CAUSED BY OTHER FUNGI 



already eaten and destroyed by insect larvae. It is never 

 perennial. 



The inner part of the fructification is mainly composed 

 of masses of parallel, very tender, richly septate, red brown 

 hyphae, filled with protoplasm. On the upper side many 

 of the masses run up into the scales that project from the 

 upper surface ; those on the lower side run down into the 



trama between the pores, and ac- 

 cording to Hartig it is the escape 

 of the contents from these hyphae 

 that gives the red colour on bruis- 

 ing. The pores are irregular in 

 shape (fig. 47), and from 0-5 to 

 2 mm. in diameter. Their depth 

 is about 5 mm. Near the stipe 

 the pores are long and labyrin- 

 thine, but the margin is barren 

 until marginal growth has ceased, 

 when pores are formed out to the 

 edge. Inside, the pores are lined 

 by the hymenium, which is com- 

 posed of basidia and various forms 

 of paraphyses. The basidia are 

 colourless or very pale yellow, 

 30-40 X 5-8 M. The spores are 

 about 4X 6 ;u (fig. 48). In addition 

 to the basidia there are numerous 

 thin-walled paraphyses and larger specialized thick-walled 

 paraphyses (cystidia). As shown in this figure the cystidia 

 are very variable in shape and size. They have deep brown 

 contents, and the large brown hyphae which carry them can 

 often be traced for some distance back into the trama. The 

 cystidia project into the pores beyond the basidia, and 

 often bear drops of liquid at their extremities to which 

 spores adhere. Thus it appears that the cystidia obstruct 

 the normal dispersal of the spores. 



When the fructifications are growing actively the spores 

 fall from them in clouds, dense enough to be seen with the 



FIG. 48. Hymenial layer 

 of Polyporus Schweinitzii, 

 showing basidia (6), basidio- 

 spores ($), paraphyses (p), 

 and cystidia (c) ( x 300). 



