MYCETOZOA. 137 



twist in all directions, as may be seen if a broken sporangium is 

 viewed under the microscope. When the sporangium wall bursts, 

 as it does on becoming quite mature and dry, this action of the 

 elaters lifts the spores as a loose mass, so that they are easily 

 blown away by the wind. 



FIG. 2 : Arcyria punicia. In the genus Arcyria the dispersal of 

 the spores is accomplished by means of a confined elastic network 

 of capillitium, which, as soon as the sporangium is matured, 

 expands to a bulk many times greater than it occupied before the 

 membranous enclosing wall was broken ; by this remarkable 

 contrivance the spores are freely exposed to the action of the 

 wind. 



If a few sporangia of the species figured are brought home while 

 still wet and unbroken and are placed on a sheet of paper in a dry 

 room, in the course of an hour or two the paper will be covered 

 with the red spores for a considerable distance round the sporangia, 

 for the slightest breath of wind carries the impalpable dust. 



FIG. 3 : Stemonitis fusca. The genus Stemonitis shows 

 again a structure beautifully adapted for the dispersal of spores. 

 Here we have no elastic network or twisted threads, but the 

 cylindrical sporangia have stiff stalks which run up the middle, 

 keeping the long column erect ; from this central axis the branch- 

 ing capillitium spreads to the surface, where it forms a net 

 enclosing the spores. The membranous wall, which was at first 

 outside the net, breaks up and disappears as soon as it dries, leaving 

 the spores in an open basket, through the meshes of which they 

 dust out and are carried away by the wind. 



FIG. 4 : Pliysarum leucopliceam. The genus Physarum is a 

 large one, containing species which differ widely from each other in 

 form : while some are symmetrical with long stalks, others are 

 sessile and of irregular shape, but the presence of lime knots or 

 vesicular swellings filled with granules of calcium carb, interspersed 

 among the delicate branching threads of the capillitium, together 

 with, in most instances, a somewhat membranous sporangium wall 

 are pretty constant generic characters. A confusion is often noticed 



