256 RESEARCHES ON FUNGI 



spores of adjacent basidia cannot touch one another. Basidia 

 bearing partly-grown and colourless spores are absent. Such a 

 black area is illustrated in the middle of Fig. 89, which shows 

 the result of a camera-lucida drawing in which all the spores were 

 sketched. In a white area, just as in a black, there are a con- 

 siderable number of spore-bearing basidia, which are separated 

 from one another by such distances as to prevent the spores of 

 adjacent basidia from ever coming into contact (Fig. 89) and which 

 are all of about the same age ; but here the spores are only partially 

 grown or, if full-grown, colourless or here and there showing but 

 a faint tinge of brown. It is evident that the black and the white 

 areas owe their appearance to the amount of pigment in the spores 

 present on each : in the black areas the spores are all black, while 

 in the white areas the spores are colourless. Now the colour and 

 the state of development of any spore are correlated, for a spore 

 is always colourless when it is young, and only acquires pigment 

 when it is nearing maturity. So far as their development is 

 concerned, basidia bearing colourless spores are comparatively 

 young, wh 1st basidia surmounted with black spores are compara- 

 tively old. We can therefore say that the generation of basidia 

 bearing spores in a black area is older than the generation of 

 basidia bearing spores in a white area. 



From the observations just described it seemed to me safe 

 to make the following deductions : (1) as the spores ripen, a white 

 area must change into a black area, (2) the spores on a black area, 

 since they are all of about the same age, must all be discharged 

 at about the same time, (3) on discharge of its spores, a black 

 area must turn into a white area, and (4) there must be areas 

 intermediate between the black and the white. 



On studying the hymenium again, I found no difficulty in 

 observing the intermediate areas. A camera-lucida sketch showing 

 black, white, and intermediate areas is given in Fig. 90. One 

 can see from the drawing that, in the piece of hymenium repre- 

 sented, waves of development are exhibited. A large black area at 

 a and c passes by means of two intermediate areas, in which the 

 spores are turning brown, into two white areas at b and d respec- 

 tively. In Fig. 89, the browning of some of the colourless spores, 



