PANAEOLUS CAMPANULATUS 267 



which have black spores but those which have brown. This being 

 so, it follows from the observations recorded above that an un- 

 magnified area, during the development of the second generation 

 of spores observed, will appear light for about 3 hours and dark 

 for about 5 hours. Since every other area has its light and dark 

 periods divided in a similar manner, and since all the areas at one 

 and the same time are in diverse stages of development, it is clear 

 that to the naked eye, on the average, the surface extent of the 

 dark areas will exceed that of the light areas in the proportion 

 of about 5 to 3. The general correspondence of this calculation 

 with the truth may be judged by the reader from an inspection 

 of Fig. 88 (p. 252). 



Successive Generations of Basidia. As soon as the second 

 observed generation of spores had been shed, a third began to 

 develop. The basidia of the third generation arose and went 

 through a series of developmental changes exactly similar to 

 those already described for the basidia of the second generation. 

 After the third generation of basidia had shed its spores, a fourth 

 generation of basidia took its place, and so on. Altogether in the 

 course of three complete diurnal periods, i.e. 72 hours, I observed 

 seven successive generations of basidia upon the same area. The 

 gradual development of the hymenium continued steadily through 

 the nights as well as through the days, so that it appeared to be 

 unaffected by light. It is perhaps almost needless to say that 

 my eye was not continuously fixed on the area under study for the 

 whole of the 72 hours : rather, observations were made at frequent 

 intervals, every hour or so. During certain brief periods when 

 I found it necessary to rest, S. G. Churchward kindly took my 

 place at the microscope. At night the gill was only illuminated 

 when it was necessary to observe, it. The temperature of the 

 laboratory was maintained at about 20 C. 



As the fruit-body grew older, the rate of development of the 

 hymenium diminished. The third generation of basidia completed 

 its development more slowly than the second, the fourth more 

 slowly than the third, and so on. The actual times between the 

 spore-discharges were noted and are given in the following 

 Table. 



