PILOBOLUS UMBONATUS 177 



When with the help of the microscope one looks down upon 

 dried discharged sporangia of Pilobolus umbonatus, P. longipes, and 

 P. Kleinii attached to a glass slide, one can at once distinguish those 

 of P. umbonatus from those of the other two species : (1) by the 

 presence of the umbo which in strong lateral illumination reflects 

 the light on one side ; (2) by the smoothness or radial wrinkling of 

 the black sporangium- wall below the umbo ; and (3) by the fringe 

 of the sporangium- wall which, as already mentioned, is transparent, 

 practically colourless, circular at its margin, and largely or quite 

 devoid of crystals (Fig. 105, I and J). 



To observe the columella whilst this is still attached to the 

 subsporangial swelling, one places a fruit- body in a drop of water 

 on a slide and one then strokes away the sporangium with a needle. 

 A columella exposed to view in this way (Fig. 88) is very bluntly 

 conical or rounded in shape, distinctly grey or bluish-grey in colour, 

 and connected at its base with the usual thin lower band of 

 sporangium-wall that separated from the rest of the sporangium- 

 wall when dehiscence of the sporangium took place. 



The columella in a dried discharged sporangium attached to a 

 glass slide can be brought into view by adding water and a cover- 

 glass, and by then pushing the cover-glass laterally. Columellae 

 brought into view in this way reveal their grey or bluish-grey colour 

 and also the narrow band of sporangium-wall attached to their free 

 margin. 



Taxonomic Description and Latin Diagnosis. — An attempt will 

 now be made to describe Pilobolus umbonatus for taxonomic purposes. 



Pilobolus umbonatus, sp. nov. Fruit-body 3-9 mm. high, arising 

 from an oval to turnip-shaped basal swelling or trophocyst which 

 may be terminal or intercalary, single or dispersed at intervals 

 along a coarse stolon-like main hypha. Stipe increasing shghtly in 

 diameter from below upwards, until just beneath the subsporangial 

 swelhng it is about 0-1 mm. in diameter. Subsporangial swelling 

 ellipsoid, in well-grown fruit-bodies about 0-65 mm. long and 

 0-46 mm. broad ; a pale orange-red band of protoplasm at the 

 junction of the stipe and the subsporangial swelling. Sporangium 

 decidedly umbonate and more or less conical, 0-21-0-23 mm. in 



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