172 THE MVXOMVCETES OF I'ICTOU COUNTV.— MOORE 



up and becomes an amoeboid body and all fuse together to again 

 form a motile plasmodium. 



Sporangia. The strucrnri' and jveculiarities of the ■•por- 

 angia capillitium and spores, in so far as illustrated bv our 

 known Xova Scotia forms, are more or less fully set out in the 

 detailed descriptions of the species iii my collection. 



In this connection it may l>e stated that in the evolution of 

 the Myxomycetes, tlie most prominent feature is the gradual 

 perfecting of the mechanical contrivances to effectuate spore 

 dispersal. The most primitive form of fructiiication must be 

 I'ogarde I as the ])lasmodiocarp, consisting of a limiting mem- 

 brane enclosing a mass of s])ores which onl^' escape by its 

 gradual breaking down. Such forms we hud in the less special- 

 ized families of the Crihrarinceoe. 



Starting from this simple form there otfshoot two main lines 

 of development exhibiting the gradual perfecting of two disunct 

 forms of adaptation for insuring effectual spore dispersal. 



The first consists in the modification of the sporangial v/all, 

 its thick(nings l)ecoming discontiniKuis so that the breaking 

 down of the Thinnei", more delicate areas facilitates the escape 

 of the enclosed spores. This line of development is exhibited 

 through the (Jrihrarias to Diciydiuin cancel! atium, where it 

 reaches its higest expression. In this species, the walls of the 

 ripe sporangium become reduced to a mere framework of ribs 

 connectefl by delicate- transverse threads, the whole structure 

 dangling on llie end of the stipe which is weak and tenuous at 

 it- u])per extremity. 



The second consists in the development of a caplllitlnm, 

 either with or without a columella. The highest forms Vvdtli 

 coluinella are found auKuig the Stemonitacew in such genera a5 

 Stemonitis, Comatricha and Ldmproderma. The most perfect 

 adaptations for securing spore dispersal, however, arc found iii 

 foinns destitute of a columella, such as the Arcyrias and Tri- 



