^902j CURRENT LITERATURE 



459 



1 



I 



proposes a large number of purely formal descriptive terms, for which 



the reader is referred to the article in question. According to Brebner, 



"the haplostele (protostele of the young stem) does not pass through 



medullated stage, but becomes crescentic after the departure of a variable 



number of leaf traces. When this stage is reached, the next leaf-trace passes 



off from the convexity of the crescent, thus causing a distinct leaf gap. Two 



mensteles are left behind with what is usually regarded as extra-stelar tissue 



between them. The crescent gap is closed, a leaf trace is given off. the gap 



is closed again, etc. By the repetition of the process, followed by branching, 



anastomosis, and increase in the number of leaf trace meristeles, at length a 



network of strands, or the dictyostele, is formed." The course of development 



appears to follow substantially that described for the Marattiaceae by P^armer, 



Hill, and Jeffrey. The author states that there is a great deal of uniformity 



m the anatomy of the Marattiaceae, all being adelosiphonic, with a greater or 



less tendency to dorsiventrality. — E. C. Jeffrey. 



DiCTVOSTELiUM MUCOROIDES, One of the Myxomycetes, was discovered 

 and described by Brefeld in 1869, since which time several investigators have 

 studied its morphology and cultural reactions. Nadson, in iSgg, asserted 

 that he had obtained it in absolutely pure culture, although he found that it 

 grew better with bacteria, and especially that a symbiosis existed between 

 the mould and B. Jluorescens lignefaciens. Potts,''^ however, has found that 

 J), mucoroides will not develop entirely free from bacteria, and that the species 

 which he isolated in connection with it was a new form, named by him Bad. 

 fimbriatMni. By a series of ingenious experiments he determined that 

 symbiosis did not take place between D. mucoroides and either Bact, 

 fimbriaium, B, fuegatherium, B, subtilis, or B. fluor, liq., i. e., that although 

 the mould derived benefit from the presence of the bacterium, its effect was 

 injurious upon the latter, which underwent extracellular digestion, appar- 

 ently by an enzyme secreted by the plasmodium. Living bacteria were 

 not necessary to D, 7nHcoroides, which could flourish, not upon the 

 metabolic bacterial products, but upon the dead organisms. Besides 

 D. 7nucorozdes, a protozoan, Amoeba nzirophila, has been found to 

 nourish itself through extracellular digestion (see Frosch, Zur Frage der 

 R^inziichtnng der Amoeben, Centr. b. Bact, 21 ^ : 1897). It is probable that the 

 same is true of many other Myxomycetes and Protozoa w^hose method of 

 nourishment has been problematical. The author made no attempt to iso- 

 late the enzyme, but carried out detailed experiments to determine the effect 

 of various non-proteid media and of light, temperature, and moisture upon 

 cultures of D. mucoroides and Bacf. fijnbriatiim. For the germination of 

 spores, oxygen, phosphate, organic substance, and water are necessary. 

 Optimum reaction is o. r per cent, to 0.2 per cent, alkaline; optimum tempera- 



"Po'JTS, Geo,, Zur Physiologie des Dictyostelium mucoroides. Flora 91 : 281- 



347-j^^j. 2. 1902. 



