84 



RESEARCHES ON FUNGI 



between / and g) ; (2) the formation of a tuck in the wall beneath 

 the edge of the convex part of the sporangium ; (3) the formation of 

 depressions or dimples in the upper part of the sporangium-wall 

 (Figs. 39 and 40) ; and (4) the contraction of the spore-mass, the 

 adherence of the spores to one another, and a change of the shape of 

 each spore from rounded to polygonal (Fig. 41). 



The existence of a tuck in the sporangium-wall of a dried 

 sporangium (Fig. 41, gr) has not been previously recorded by any 

 other observer, and it was discovered only as a result of a detailed 



Fig. 40. — Pilobolus longipes. Discharged sporangia, from a pure culture, attached 

 to a sheet of glass, photographed by reflected light. To show the characteristic 

 wrinkles developed in the sporangium-wall as the sporangia dried up, Mag- 

 nification, 60. 



investigation on dried and drying sporangia. If a sporangium which 

 has dried on a glass surface is pried loose from its substratum, the 

 fringe of the sporangial wall and the gelatinous ring are left behind 

 on the glass, but the wall- tuck remains attached to the under side 

 of the sporangium. The tuck extends centripetally to a distance of 

 about one-fifth to one-quarter the radius of the sporangium as a 

 whole. A sporangium was allowed to land on a cover-glass and dry 

 there, and then the cover-glass, with the sporangium beneath, was 

 set on a drop of sulphuric acid on a glass slide (c/. Fig. 35). With 

 the microscope the action of the sulphuric acid could be followed. 

 The acid dissolved away the sporangium- wall progressively from the 

 free edge inwards, until the whole wall disappeared leaving the mass 

 of spores behind. The fringe of the wall disappeared first, and soon. 



