MACROSCOPIC OBSERVATIONS 91 



from time to time, but the air of the greenhouse was dry. It 

 seemed of interest to find out whether or not moist air causes a 

 diminution in the rate of spore-fall. Accordingly, the log was 

 removed to the Hymenophyllum house after this had been so 

 well syringed that its warm atmosphere appeared to be saturated 

 with moisture. The spores, however, continued to fall for two 

 hours quite as rapidly as in the dry greenhouse. Wreaths and 

 curls of spores floated slowly away from the fruit-body. The 

 log was then taken back to its former dry situation, where the 

 visible fall of spores went on unabated. Ordinary variations in 



Fig. 36. — Spores leaving a fruit-body of Polyporus squamosus and being carried 

 away by slow air movements. \ natural size. 



the hygroscopic state of the atmosphere, therefore, do not appear 

 to affect appreciably the fall of the spores. 



Some very young fruit-bodies which just showed the earliest 

 indications of the development of hymenial tubes were found 

 growing upon a log of wood in the open. The log was immediately 

 removed and placed in a dark room. Under these conditions 

 the hymenial tubes developed in a normal manner (c/. Figs. 5, 6, 

 and 7, pp. 29, 32, and 33), and on the fourth day abundant spore- 

 clouds were produced. These continued to fall for eleven days, 

 at the end ^f which time the fruit-body had begun to wither. 

 The production and liberation of spores, therefore, appear to be 

 carried on quite independently of light. 



The hymenial tubes begin their development as saucer-shaped 

 structures on the underside of the pileus. The walls of the tubes, 

 which are positively geotropic, then grow vertically downwards 

 for some days. By elongating in this manner, the tubes, although 

 often shorter, may attain a length of a centimetre (Fig. 7, p. 33). 



