MYXOGASTRALES 



147 



feeding on bacteria it absorbs liquid nutriment rapidly, and 

 soon divides itself into two organisms similar to itself, this division 

 continuing with greater or less rapidity until a large number, 

 usually a swarm, of these bodies are developed, each continuing 

 to feed on its supply of nutriment and increasing to a certain size 

 before division. When a certain stage of this multiplication has 

 been reached, the swarm commences a reverse process, by a 

 union into a mass which ultimately gathers all into its train, add- 

 ing to itself any stragglers that may be picked up along its line of 

 march. When the individuals are thus absorbed into the plas- 

 modium they lose their cilia and the whole plasmodium progresses 

 from place to place by a seemingly creeping motion which is 

 really the result of a streaming process that occurs within the pro- 

 toplasm, alternately producing a forward and backward flow. 

 Many species form tongue-like interlacing masses, in which the 

 alternating currents, stronger or weaker, determine the direction 

 of motion of the mass. By cultivating the plasmodium in a moist 

 chamber on wet decaying wood, it is an easy matter to make a 

 demonstration of this streaming motion on glass so that the move- 

 ment may be made the direct object of microscopic examination. 

 At almost any time during summer and autumn masses of this 

 network of yellowish protoplasm may be found by tearing open 

 soggy decaying logs in the forest. 



When the plasmodium has reached a certain size it creeps up 

 to a convenient more or less exposed position on a log or stump 

 or spreads itself over violet leaves, or creeps up the stems of 

 grasses, or clambers over beds of moss or even climbs trees, in 

 order to secure a favorable position in which to produce its spores 

 where they may be more effectively disseminated. In a few 

 cases the whole mass surrounds itself with a more or less tough wall 

 and the interior portion then divides itself into innumerable dust- 

 like spores each one of which is itself surrounded by a thin but 

 impervious wall so as to maintain its contents from completely 

 drying up.* In a greater number of species the plasmodium 



^ Three methods of producing spores result in bodies which receive 

 special names : 



I. Stalked or sessile sporangia are produced about centers in the plas- 

 modium as the protoplasm assumes an upward direction. These sporangia 

 are of a definite shape for each species and usually quite uniform in size. 



