DEVELOPMENT OF PLANTS 153 



dependent upon organic food. Plants that feed in this way are 

 called saprophytes. Since the plasmodium is not surrounded by 

 a cell wall feeding becomes a simple matter. The jelly-like 

 mass engulfs the decaying particles or other foods and after 

 digesting the nourishing portions leaves behind the worthless 

 parts as it creeps along. As the plasmodium approaches the 

 final stage of its life, its nature appears to change completely, 

 for now it avoids moisture and seeks the light. It creeps to 

 the surface of the wood or leaves in which it has been 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 network 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 

 ii 



