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RESEARCHES ON FUNGI 



the sporangium and moved laterally so as to disperse the spores in 

 the water. The cover-glass was now removed. Then pieces of the 

 sporangial wall were lifted from the jelly and the jelly was moved 

 about until it was free from spores. From three of the sporangia 

 treated in this way as many complete rings of jelly were obtained 

 (Fig. 38). It is clear that in a sporangium the jelly does not extend 

 over the top of the columella but is annular in form. 



At the moment a sporangium with an attached drop lands upon 



a grass-leaf or other object, its ring 

 of jelly is fully distended, the 

 cavity of the cone-shaped columella 

 is filled with cell-sap, and the con- 

 tents of the sporangium (spores 

 and substance lying between them) 

 are very watery. Immediately there- 

 after, the drop and the sporangium 

 begin to lose water by evaporation 

 and, in the course of a few minutes, 

 they become air-dried. From the 

 flattened drop there are deposited 

 on the substratum amorphous par- 

 ticles and branched crystals, which 

 form a halo around the sporangium 

 (Figs. 33-35, pp. 77-79). As the 

 sporangium dries, the gelatinous ring 

 contracts to a very thin hard flat film (Fig. 35, No. 2, and Fig. 41,6) 

 which sticks the sporangium tightly to the surface of the object on 

 which it lies. As the gelatinous ring dries and flattens, the pale 

 radiately-split fringe of the sporangial wall settles down on the top 

 of the jelly and thus comes to lie parallel to the surface of the sub- 

 stratum (Figs. 39 and 41). The cell-sap in the cavity of the colu- 

 mella is bounded by the conical wall of the columella and the surface 

 of the substratum, and it is free from air-bubbles As this ceU-sap 

 evaporates, the columella cavity (into which air cannot enter) 

 necessarily becomes more and more contracted, with the result that 

 the columella becomes compressed both laterally and from above 

 downwards. The lateral compression results in the free edge of the 



Fig. 



38. — Pilobolus longipes. A 

 gelatinous ring isolated from a 

 sporangium that had been 

 stroked away from the spor- 

 angiophore and columella under 

 water. Magnification, 75. 



