158 RESEARCHES ON FUNGI 



of the glass simultaneously, the drop will flatten out on the surface 

 of the glass and force the sporangium to take up its characteristic 

 position on the glass by the same means as described under (4). 



(5). If the sporangium is directly in front of the drojJ of cell-sap 

 so that the axis of the projectile is perpendicular to the surface of 

 the glass, the sporangium will strike the surface of the glass first 

 and be momentarily overwhelmed and imprisoned between the 

 glass and the drop ; but, immediately thereafter, owing to the 

 lateral spreading of the drop and to the unwettability of the spor- 

 angium-wall, it is probable that the thin water-film covering the 

 sporangium will break in such a way as to cause the drop to pull 



Fig. 77. — Pilobolus longipes. Diagram showing in lateral view the 

 position of a discharged sporangium after landing on a sub- 

 stratum. A, normal position ; sporangium attached to the sub- 

 stratum by its gelatinous ring. B and C, abnormal positions. 

 B, sporangium resting on its side, gelatinous ring and spores partly 

 displaced from their normal position. C, sporangium upside 

 down ; it has no gelatinous ring. Magnification, about 44. 



the sporangium round through an angle of 180° and so cause the 

 sporangium to reverse its former position, and take up the nor- 

 mal position for a discharged sporangium, namely, that shown in 

 Fig. 74, B. 



Summing up the explanation given above, it may be said in 

 general terms that a sporangium settles on any object it may strike 

 by its gelatinous side because its gelatinous side is wettable and its 

 convex side covered by the black sporangial wall is unwettable. 

 and because the sporangium is accompanied to its destination by 

 a large drop of cell-sap. 



Very occasionally, a sporangium lands on the side of a glass 

 plate or other object so that it comes to rest in an abnormal manner, 

 i.e. so that its gelatinous side is not flattened out against the object 

 struck and so that it rests on its side (Figs. 77, B, and 78, A) or on 



