138 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 greatlv increased in number by division, becomes surrounded 

 by a wall, thus forming the spores. Usually a portion of the sub- 

 stance of the young sporangium is transformed into simple or 

 branching threads or tubes, collectively called the capillitium (Fig. 

 90). In several of the genera the wall of the sporangium is 

 formed of a net work of the capillitium (Fig. 88). These threads 

 are hygroscopic and their constant 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 club- 

 root. 



There are several groups of low types of plant and animal 

 life J:hat are suggestive of relationship with the slime moulds. 

 The most important among these, the myxobacteriales, have been 

 made known by Taxter. 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. As far as known the en- 

 tire life history is purely an asexual existence. It is possible, 

 however, that the purpose of reproduction may be effected among 



