146 SPORANGIA OF THE SLIME MOULDS 



growing and forms the characteristic bodies seen in Figs. 87, 88. 

 These sporangia are formed by the outer part of the Plasmodium 

 hardening into a wall, while each of the inclosed nuclei, which 

 have greatly increased in number by division, becomes sur- 

 rounded by a wall, thus forming the spores. Usually a portion 

 of the substance of the young sporangium is transformed into 

 simple or branching threads or tubes, collectively called the capil- 

 litium (Fig. 90). In several of the genera the capillitium forms 

 a net work within the delicate walls of the sporangia and owing 

 to the early breaking down of the wall, the feathery frame alone 

 remains (Fig. 88). These threads are hygroscopic and their con- 

 stant motion assists in stirring up the spores and exposing them 

 gradually to the wind as soon as the wall of the sporangium 

 ruptures. A somewhat simpler type of slime mould lives as a 

 parasite in the roots of turnip, cabbage and cauliflower producing 

 a destructive disease known as clubroot. 



There are several groups of low types of plant and animal 

 life that are suggestive of relationship with the slime moulds. 

 The most important among these, the myxobacteriales, have been 

 made known by Thaxter. They are minute plants, very sugges- 

 tive of the next group, the bacteria, but associated in definite 

 structures that resemble the sporangia of the slime moulds and 

 also of certain fungi. On the other hand, certain aquatic forms, 

 as Protomyxa, with a life history very similar to that of the 

 slime moulds, intergrade almost perfectly towards simple ani- 

 mal types, as the protozoans, of which the common amoeba is 

 an example. 



Thus we see that the life history of these plants is a very 

 simple one. By the formation of sporangia numerous dust-like 

 spores are produced that are capable of germinating and form- 

 ing zoospores that increase rapidly by division. The aggrega- 

 tion of the zoospores results in the formation of the Plasmodium 

 which after a time completes the life history by creeping upon 

 suitable dry objects and forming sporangia. The mingling of the 

 zoospores in the formation of the plasmodium is not a sexual 

 process, since the nuclei do not fuse, but Olive has shown that 

 the spores are formed in the same manner as in plants character- 



