Uniied States Species of LTjcoperdon. 2S9 



dium. Thej therefore form a central mass more or less 

 distinct from the rest and are then called the columella. 



The columella is usually of a someNvhat conical shape, 

 but sometimes it is nearly globose. It may be detected 

 in the mature plant by carefully making two opposite slits 

 in the peridium, extending them from the apex nearly or 

 quite to the base, and then opening the two hemispheres 

 thus formed, the uncut base acting as a hinge on which 

 the halves may turn. The coluuiella if present will be 

 seen projecting from the base in the centre of the cleft. 

 The slits are best made with a pair of small sharp scissors 

 as care should be taken not to disturb the natural position 

 of the filaments more than is necessary. 



In the mass the capillitium and spores appear to be uni- 

 formly and similarly colored, but often if the filaments 

 are cleared of the spores they are seen to be paler in color. 

 Rarely they are darker. The color of the capillitium and 

 spores might be used as a character for grouping our spe- 

 cies in subsections. 



The spores in all our species are nearly or quite globose. 

 They vary in size in the different species from .00016 to 

 .00025 of an inch in diameter. The olive tinted spores 

 in nearly all the species are smooth and about .00016 

 of an inch in diameter, but the purple tinted ones 

 are always rough or echinulate and generally larger, vary- 

 ing from .0002 to .00325 of an inch broad. It is perhaps 

 needless to say that the size of the spores docs not at all 

 depend on the size of the plant that produces them. The 

 spores of the Giant pufi:-ball, the largest one of the genus, 

 are but .00016 of an inch in diameter, while those of the 

 Smooth puff-ball, which is scarcely more than an inch in 

 diameter, are about .00025 of an inch broad. The color 

 of the spores maybe ascertained by ejecting a small quan- 

 tity of them on white paper or by opening the peridium 

 and exposing them to view. 



