SLIME MOULDS (mYXOMYCETES) 1 5 



result of the progressive cleavage in furrowing is the formation of uninu- 

 cleated rounded spores. They lie packed between the capillitial 

 threads. 



Most genera of slime moulds have a capillitium (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 capilUtium extends from the 

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

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

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

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

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

 then the so-called lime knots. In Dictydium, purplish-red granules 

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

 as dictydin granules. The formation of the capillitium in certain 

 myxomycetes has been investigated by Harper and Dodge.^ They 

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

 vacuoles from which the capillitial thread is formed and that radiating 

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

 process of intraprotoplasmic secretion. These radiating fibrils sug- 

 gest rather strongly that they are cytoplasmic streams which are 

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

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

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

 but along internal plasma membranes, rather than external. The 

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

 capillitial vacuole runs longitudinally. Strasburger's earlier observa- 

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

 he described the capilUtium 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 capillitial 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, xx\'iii: i-i 8, January, 1914. 



