PANAEOLUS CAMPANULATUS 307 



the number of basidia on a square mm. was about 6,100 ; on a 

 square cm. 610,000 ; and on 88 square cm., i.e. on all the gills 

 taken together, 53,680,000. From this, reckoning four spores to 

 each basidium, it was calculated that the total number of spores 

 which the fruit-body had produced was approximately 215,000,000. 

 If we take the number of wasted spores as forming 3-8 per cent, 

 of this number, the absolute number of wasted spores on the whole 

 fruit-body was about 8,000,000. Subtracting this from the whole 

 number of spores produced, we find that 207,000,000 spores were 

 liberated. We may conclude, therefore, that even when the wasted 

 spores left on the gills amount to millions they may yet be very 

 few compared with the vast number which have been set free. 



We may now enquire into the causes which may prevent full- 

 grown spores from being properly liberated. If a gill is displaced 

 so that its median plane is no longer vertical but inclined at an 

 angle of several degrees, then a spore which has been shot out at 

 one point on the upper side of the gill will soon strike the gill 

 again at a lower point. After falling on a gill in this way, a spore 

 never gets free again : it adheres tightly to the hymenium until 

 the fruit-body decays. An illustration showing the effect of 

 inclining gills shaped like those of Panaeolus campanulatus has 

 been given in Volume I, Fig. 12, p. 40. When a large number 

 of spores fall on to the upper side of the gill of a displaced fruit- 

 body, the gill on its upper side becomes, in the words of the 

 field-botanist, " powdered with the spores." In the fruit-body of 

 Panaeolus campanulatus which was investigated the median planes 

 of the gills were properly adjusted in space, so that this powdering 

 could not occur. 



On almost all large fruit-bodies of Hymenomycetes growing in 

 woods in the warm days of autumn one may find Fungus Gnats, 

 Mites, or Springtails. These crawl over the gills. Doubtless they 

 displace many of the spores, for they are bound to touch these 

 in their peregrinations. However, the extent to which crawling 

 insects are a cause of the accumulation of wasted spores on gills, 

 etc., in nature, requires further investigation. So far I have made 

 no special observations in connection with this matter. 



When the wind is blowing strongly in one direction, the spores, 



