The Plant Kingdom - 603 



Fig. 31-7. The Plasmodium of a slime mold (Cribraria) creeping over the surface of 

 an agar nutrient medium in a Petri dish. Note the irregular lobose form of the 

 Plasmodium, which is quite typical of the Myxomycophyta generally. (Photo by 

 G. W. Martin; from The Plant World, by Fuller and Carothers. Holt, Rinehart and 

 Winston, Inc.) 



eter and sometimes they are almost micro- 

 scopic. 



Each spore of the slime mold, typically, 

 gives rise to four naked cells, capable of 

 active amoeboid movement and often pos- 

 sessing one or more flagella. Each of these 

 swarm cells, which are called myxamoebae, 

 usually divides a number of times, producing 



more myxamoebae. Eventually, however, 

 the cells fuse in pairs, each pair forming one 

 zygote. Then the zygote gives rise to the 

 Plasmodium of the next generation. 



Some myxomycophytes are parasitic and a 

 few are important in relation to plant dis- 

 eases. For example, the club-root disease of 

 cabbages and the powdery-scab disease of 



Fig. 31-8. Sporangia of two different slime molds, growing on tree bark. Although 

 the sporangium of a myxomycophyte is seldom bigger than a pinhead, the size, 

 shape, colors, and markings are distinctive for each species. Those on the left are of 

 Badamia foliicola, and those on the right are of Physarum globuliferum. (Photos by 

 Richard Benjamin; from The Plant World.) 



