COPRINUS STERQUILINUS 223 



A spore which has attained full size but is as yet colourless is 

 connected by a channel through its hilum and the neck of the 

 sterigma with the basidium-body from which it is receiving proto- 

 plasm and food materials. If now such an unripe spore is broken 

 away from its sterigma under water, there is a hole in its wall at 

 the hilum. Nevertheless, the spore does not collapse but remains 

 living and apparently turgid ; for one can strongly plasmolyse it 

 with a solution of 10 per cent, potassium nitrate and then deplas- 

 molyse it with water. This observation indicates that a spore, 

 when shot away from its sterigma, does not require to have its 

 hilum closed by a membrane. Closing walls at the hilum of a 

 spore and at the end of the sterigma at the moment of spore-dis- 

 charge have not as yet been definitely seen and possibly do not 

 exist. 



The number of spores on a fruit-body having a pileus 4 cm. high 

 in the unexpanded condition, i.e. on a fruit-body of medium size, 

 was estimated in the following manner. With the microscope it was 

 found that on an area of the hymenium measuring 0-08 square mm. 

 there were 58 basidia. Reckoning 4 spores to each basidium, it 

 was then calculated that on 1 square mm. of hymenial surface 

 there were 2,900 spores. After the area of the exterior surfaces of 

 the gills had been measured, it was estimated that the hymenium 

 had an area of 34,496 square mm. From these data it was calculated 

 that the total number of spores on the whole pileus was 100,038,400 

 or, in round figures, 100,000,000. This number of spores, although 

 so large when considered by itself, is relatively small ; for a fruit- 

 body of Coprinus comatus ^ was calculated to have produced 

 5,000,000,000 spores and a fruit-body of Psalliota campestris ^ 

 16,000,000,000. The small number of spores produced by Coprinus 

 sterquilinus as compared with C. comatus is due to the fact that, 

 in the former species, the fruit-body not only has a much smaller 

 amount of hymenial surface but also a smaller number of basidia 

 on each unit area of its hymenium. The relatively small number 

 of basidia on each unit area of hymenium is correlated with the 

 unusually large size of the basidia and their spores. A basidium 

 of C. sterquilinus, since it is so much larger than a basidium of 

 1 Vol. i, 1909, p. 83. 2 Vol. ii, 1922, ]ip. 40.3-404. 



