128 



RESEARCHES ON FUNGI 



it has been ascertained by counting the successive tube-layers, is 

 summarised in the following Table. 



Age of Oldest Known Fruit-bodies of Certain Polyporeae. 



The Hymenial Tubes. The fruit-body of Fomes applanatus is 

 bracket-shaped and broadly attached to its woody substratum. 

 Its broad attachment and its remarkably hard upper crust serve 

 to keep the hymenial tubes fixed permanently in one position. 

 The hymenial tubes are very long and yet extremely narrow. In 

 one large fruit-body, in one layer, I found them to be 12 mm. long, 

 except toward the margin of the pileus where they became pro- 

 gressively shorter, but they were only 0-17 mm. in internal diameter. 

 In another very large three-year-old fruit-body (Fig. 48, p. 131), 

 where the internal diameter of the tubes was also 0-17 mm., the 

 length of the tubes (except near the margin of the pileus) varied 

 in the first tube-layer from 9 to 12 mm., in the second from 19 to 

 28 mm., and in the third from 18 to 20 mm. In large well-grown 

 fruit-bodies, therefore, the majority of the hymenial tubes vary 

 in length from about 10 to 20 mm. and exceptionally attain a length 

 of 28 mm., while their average internal diameter is only about 

 0-17 mm. From these data it can be calculated that the ratio of 

 tube-length to tube-breadth in large fruit-bodies varies from about 

 60 to 120 and, exceptionally, is as great as 170. Now, as the 

 hymenial tubes are relatively so very long and yet so very narrow, 

 it is of high importance for the escape of the adhesive spores that 

 the cylindrical lumen of each tube shall have its axis perfectly 

 vertical ; for the least deviation from this direction, i.e. a deviation 

 of 1 or even less, will cause the spores shot from the basidia in the 

 upper and middle parts of each tube into the intratubular cavity to 

 strike the sides of the tube during their fall and to adhere there 



