PANAEOLUS CAMPANULATUS 273 



fact that they are concealed within the concavity, which for optical 

 reasons escapes observation. There can be no doubt that such an 

 exhausted and shrunken basidium as has just been described is 

 no longer living ; and we are justified in concluding that a basidium 

 dies within about twenty minutes to half an hour after shedding its last 

 spore. 



The sterigmata, after being dragged downwards into the con- 

 cavity at the end of the shrunken basidium, become more or less 

 melted down into mere stumps (Fig. 93, C, a, c, d, h, j, Jc ; also 

 Fig. 94, A and B, p. 276). Their remains continue to persist as 

 small lumps of refringent matter, which do not disappear until the 

 hymenium is utterly exhausted and begins to undergo putrefaction. 



If a gill which has been discharging spores is placed flat on a 

 glass slide and covered with a cover-glass, and if water is then 

 allowed to run between the cover-glass and the upper hymenium, 

 it may be observed that the water, as it progresses over the 

 hymenium, often leaves behind a tiny bubble of air over the top 

 of each exhausted basidium (Fig. 93, B). The same effect can 

 be obtained with glycerine or chlor-zinc iodine. The bubbles are 

 caught in the concavity at the end of each basidium-body. Such 

 bubbles may help one in distinguishing exhausted basidia in both 

 surface and cross-sectional views of the hymenium. 



A study of exhausted basidia was made upon the gill of a fruit- 

 body of Panaeolus campanulatus obtained in the wild state from a 

 field, and the accompanying drawing (Fig. 93, C) shows the appear- 

 ance of a number of these elements. In each case the rim of the 

 concavity at the end of the exhausted basidium can be clearly seen, 

 and from its somewhat irregular shape the conclusion may be drawn 

 that the concavity is not very symmetrical. It was necessary to 

 focus downwards from the rim in order to see the bottom of the 

 concavity and so perceive the four sterigmatic stumps. The latter 

 are aggregated in various ways in different basidia, doubtless on 

 account of irregularity in the disposition of the walls of the different 

 concavities. 



An exact knowledge of the nature of exhausted basidia is of 

 great importance for our investigation of the structure of the 

 hymenium, for it enables us to tell with certainty whether a hymenial 



