150 RESEARCHES ON FUNGI 



gium takes up a position at or near the centre of the drop with its 

 gelatinous side turned toward the object struck as shown in Fig. 74, B. 

 The water in the drop and in the sporangium then evaporates, in 

 consequence of which the sporangium becomes fixed to its sub- 

 stratum by its gelatinous band and surrounded by a halo of tiny 

 particles precipitated from the drop of cell-sap (Figs. 72 and 73). 

 As the sporangium dries up, its content of spores and its band of 

 jelly shrink to such an extent that the free pale edge of the black 

 sporangial w^all comes into contact with the surface of the substratum. 

 Therefore, after a sporangium has landed on a blade of grass or 

 other herbage and has dried up, it is very firmly attached to its 

 substratum and, at the same time, its spores are all protected 

 from the light and from mechanical displacement by its tough 

 black wall. 



The rule for the mode of landing of a sporangium, already briefly 

 stated, may be re-stated more precisely as follows : a sporangium 

 lands on any object which it happens to strike — no matter what may 

 be the velocity of the sporangium when it strikes and no matter 

 whether the surface of the object looks upwards or downwards or 

 is vertical — so that, with rare exceptions, its under gelatinous side 

 is turned toivard the surface of the object and its upper black convex 

 side away from the surface of the object. This remarkable rule has 

 long been known, for it was enunciated by Coemans^ in 18G1 and 

 discussed by Grove ^ in 1884. Coemans examined 413 sporangia 

 which had fallen on to a sheet of white paper set out to receive 

 them and he found that all but three of them had their gelatinous 

 sides turned downwards toward the paper. The three exceptional 

 sporangia were upside down and rested on their black sporangial 

 walls. Some observations of my own on the landing of sporangia 

 on the under side of sheets of glass, when the sporangia were travel- 

 ling at various speeds, will now be recorded. 



Some fruit-bodies of Pilobolus longipes, attached to a small 

 mass of dung on which they were growing, were placed upright in 

 a compressor cell, so that their sporangia were only about 5 mm. 



^ E. Coemans, "Monographic du genre Pilobolus," Mem. cour. et des Sav. etrang. 

 Acad. roy. de Belgique, T. XXX, 1861, p. 59. 

 2 W. B. Grove, loc. cit., j). 17. 



