INTRODUCTORY 7 



is ruptured and the protoplasmic content escapes as a zoospore indis- 

 tinguishable so far from an amoeba, 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 

 flagellate cilium, and so acquire power of more rapid locomotion. 

 The zoospores, whether ciliate or not, thus enjoy independent ex- 

 istence and are capable of continuing such existence for some time, 

 assimilating, growing, and even reproducing themselves by simple 

 fission, over and over again. This takes place, of course, only in the 

 presence of suitable nutrient media. 



Nevertheless the spores of many species germinate quickly simply 

 in water, and a drop suspended in the form of the ordinary drop- 

 culture on a cover-glass affords ample opportunity. In the course 

 of time, usually not more than two or three days, the swarm spores 

 cease their activity, lose their cilia, and come to rest, exhibiting at 

 most nothing more than the slow amoeboid movement already referred 

 to. In the course of two or three days more, in favorable cases, the 

 little spores begin to assemble and flow together; at first into small 

 aggregations, then larger, until at length all have blended in one 

 creeping protoplasmic mass to form thus once again the Plasmodium, 

 or plasmodial phase with which the round began. Small plasmodia 

 may generally be thus obtained artificially from drop-cultures. Such, 

 however, in the experience of the writer, are with difficulty kept alive. 

 Hay infusions, infusions of rotten wood, etc., may sometimes for a 

 time give excellent results. 



The spores of Didymium crustaceum were sown upon a heap of 

 leaves in autumn. An abundant display of the same species followed 

 in the next June ; but, of course, the intervening phases were not 

 observed. The most satisfactory studies are obtained by plasmodia 

 carefully brought in directly from the field. A Plasmodium that ap- 



germinates in tap-water at temperature 70°-80° F. in 12-15 hours fresh from 

 the field. Fuligo ovata spores were all swarming in about one hour at the 

 same temperature. Jahn {Myxomycetcnstudien; Ber. der Deutschen Bot. 

 Ges. Bd. XXIIL, p. 495) finds that the germination in some cases as Stemo- 

 nitis species, is hastened by wetting, then drying, then wetting again. 



Pinoy thinks microbes aid in germination {Bull. Soc. Myc. de France T. 

 XVIII.). 



