The Myxomycetes of Eastern Iowa. 105 



The transition from phase to phase requires, as intimated, 

 no great length of time. Tilniadocke gyrocephala completed 

 the transition from vegetative to fruiting phase in less than 

 18 hours. 



The germination of the spores ensues closely upon their 

 dispersal or maturity and is unique in many respects. The 

 wall of the spore is ruptured and the protoplasmic content 

 escapes as a zoospore indistinguishable so far from an amceba, 

 or from the zoospore of our Chytridiaceous fungi. This 

 amoeboid zoospore is without cell-wall, changes its outline, 

 and moves slowly by creeping or flowing from point to 

 point. At this stage many of the spores assume each a flag- 

 ellate cilium and so acquire power of more rapid locomotion. 

 The zoospores whether ciliate or not thus enjoy independent 

 existence and are capable of continuing such existence for 

 some time, assimilating, growing, and even reproducing them- 

 selves by simple fission, over and over again. This takes 

 place, of course, only in the presence of suitable nutrient media. 

 In the course of time, usually not more than two or three 

 days (Zopf), the swarm-spores cease their activity, lose their 

 cilia and come to rest, exhibiting at most nothing more than 

 the slow amoeboid movement first referred to. In the course 

 of two or three da3^s more, the little spores begin to assemble 

 and flow together; at first into small aggregations, then 

 larger, until at length all have blended in one large creeping 

 protoplasmic mass to form thus once again the plasmodium, 

 or plasmodial phase with which the round began. 



With such a life-history as that thus briefl_v sketched, it is 

 small wonder that the taxonomic place of the Slime-moulds is 

 a matter of uncertainty, not to say perplexity. So long as 

 men studied the ripened fruit, the sporangia and the spores, 

 with the marvellous capillitium there seemed little difficulty; 

 the Myxomycetes were fungi, related to the puff-balls, and in 

 fact to be classed in the same natural order. The synonomy 

 of some of the more noticeable species affords a very interest- 

 ing epitome of the history of scientific thought in this par- 



