Heart Bot of Pimroxylon utile (Sneezewood). 221 



In the vessels I have not observed the fungus to bore directly through 

 the walls, and here they appear to follow the pits (Fig. 12 (6) ), which are 

 abundant. Prom what has been said above it will be evident that the growth 

 of the fungus longitudinally through the continuous vessels ■ and the 

 wood prosenchyma will be more rapid than laterally, in which latter case the 

 hyphae have to bore their way through the walls of the wood cells or are else 

 dependent on pits. 



Von Schrenk * has pointed out that the formation of sheets is largely 

 dependent on the resistance of the wood cells, and whether they are closely 

 packed or not, and as pointed out by him for Bolinia Pseudacacia, so I hold 

 the same to be a very plausible theory also for the sheets formed in 

 Ptseroxylon utile. 



Von Schrenk t has reported that the common form of destruction in 

 Bohinia is for the wood cells to break up into small pieces owing to their 

 walls being perforated by hyphae. The smallest pieces were shown to be 

 wood, thus indicating that the destruction does not pass through the 

 cellulose stage. 



In the material of Ptseroxylon utile examined I have never come across 

 any small pieces of unaltered wood. The destruction here appears invariably 

 to pass through the cellulose stage. In between delignified wood cells I have 

 at times come across elements, especially vessels, which still gave lignin 

 reactions, but these were never isolated into small pieces. The walls of the 

 vessels are particularly resistant. 



Desceiption of the Fungus. 



The fructifications or sporophores of Fames rimosus are among the most 

 conspicuous of the so-called " shelf " fungi which grow on living trees. They 

 vary in shape, size, etc., and especially does this appear to be the case with 

 sporophores obtained from' different hosts. 



On Ptaeroxylon utile they are usually hoof -shaped (Pig 1) or applanate, 

 and the sizes most frequently met with vary between 2-4-14 x 3-5-7'5 x 

 l'6-5 cms. In young specimens the upper surface is smooth and fulvous, 

 but with age it becomes concentrically sulcate and very much cracked or 

 jagged. The cracks do not penetrate far into the mass of the sporophore, 

 and are usually limited to the outer hard surface which in this fungus is not 

 encrusted. With age the surface colouring varies between dark brown and 

 purplish-black, and older specimens are frequently covered with moss, etc. 

 The most recent layers, which form the front of the sporophore, are charac- 



* Schrenk, H. von, "A Disease of the Black Locust {Rohinia Pseudacacia)," 

 Miss. Bot. Gdn., Twelfth Ann. Eep., 1901, p. 21. 

 t Op. cit., p. 26 



