424 RESEARCHES ON FUNGI 



into a concavity which is forming at the end of each basidium- 

 body. Soon the sterigmata will melt down to stumps and then 

 these basidia will resemble the other past-generations basidia, a a, 

 scattered throughout the Figure. The basidium w is just about 

 to discharge the second of its two spores, the first having already 

 been shot away leaving behind a stiff but naked sterigma. As a 

 preliminary to the discharge of the second spore, a drop of water 

 has been excreted at the spore-hilum within the last ten seconds. 

 The drop is almost of maximum size, which fact indicates that the 

 spore should be violently propelled from its sterigma within the 

 next two seconds. The spores on all the other basidia at the extreme 

 left edge of the black area should be shot away within about half 

 an hour. The successive discharge of all the spores on the black 

 area, proceeding from the left to the right of the Figure, might 

 take an hour and a half or two hours. If one could watch the 

 gradual disappearance of the spores in this way, one would perceive 

 that the basidia indicated by the series which bear the numbers 

 1 to 7 would be continuing their development, so that the area 

 which is now dark would gradually again come to be spore-bearing, 

 proceeding from left to right. Thus, for instance, the basidium 

 no. 6 would be observed to begin developing its spores within a 

 few minutes of the moment of discharge of the last of the six spores 

 on the three present-generation basidia with which it is now sur- 

 rounded. If we could watch the basidium no. 6 developing its 

 spores, we should find that, during the early stages of its develop- 

 ment, the spores on basidia nos. 1 and 2 would undergo pigmenta- 

 tion, those on nos. 3 and 4 would grow to full size, and those on 

 no. 5 would grow to nearly full size. It is thus clear that, as the 

 wave of development passes across the piece of hymenium, a great 

 many basidia are undergoing progressive and synchronous changes, 

 all leading to the climax of spore-discharge. Everywhere through- 

 out the finely mottled surface of the hymenium, on every gill, 

 waves similar to the one just described are moving ; but the 

 movements are in various directions. Sometimes a series of waves 

 following one another in regular succession moves over several 

 light and dark areas in a straight line in one direction ; but more 

 often the waves clash, move apart from one another, or interfere 



