SLIME MOULDS (mYXOMYCETES) 1$ 



result of the progressive cleavage in f urrowin,^ is the formation of uninu- 

 cleated rounded spores. They he packed between the capillitial 

 threads. 



Most genera of slime moulds have a capiUitium (Figs. 2 and 3) 

 consisting of a system of threads, and as we have seen, it appears be- 

 fore the spores are formed. When the capiUitium extends from the 

 base of the sporangium, it is associated with a columella (Fig. 2). It 

 differs widely in the dififerent genera of the groups. In some genera, as 

 Trichia and Arcyria, the capiUitium consists of free threads, or elaters. 

 In those genera in which calcium carbonate is present in the sporangia, 

 it is found in the capiUitium usually when several threads meet forming 

 then the so-caUed hme knots. In Dictydimn, purplish-red granules 

 are imbedded in the threads of the false capiUitium and are known 

 as dictydin granules. The formation of the capiUitium in certain 

 myxomycetes has been investigated by Harper and Dodge.^ They 

 find that the capiUitium is formed by the deposit of materials in the 

 vacuoles from which the capiUitial thread is formed and that radiating 

 threads run out from the larger granules which are deposited by the 

 process of intraprotoplasmic secretion. These radiating fibrUs sug- 

 gest rather strongly that they are cytoplasmic streams which are 

 bringing materials for the formation of the capillitial wall and its thick- 

 enings which are laid down sometimes as spirals, suggesting that the 

 process is comparable to the ordinary processes of cell-waU formation, 

 but along internal plasma membranes, rather than external. The 

 relation of the fibrils to the capillitial granules is best seen where a 

 capiUitial vacuole runs longitudinally. Strasburger's earher observa- 

 tions are confirmed by the recent work on capiUitial formation, when 

 he described the capiUitium of Trichia fallax as originating in vacuolar 

 spaces in the cytoplasm which elongate and take on the tubular form 

 of young capillitial threads, while the formation of the wall and spiral 

 thickenings are due to the deposition of granules as intraprotoplasmic 

 secretions consisting of microsomes of the membranogenous type. 

 Where the capiUitial threads are solid they may be called stereone- 

 mata; where hollow, coelonemata. 



The spores are discharged from the sporangia, and if they find a 

 suitable medium in which to grow,- such as free water, they give rise to 

 swarm cells, as amoeboid bodies, or myxamoebse. These soon acquire a 



^Annals of Botany, xxviii: 1-18, January, rQi4. 



