274 



PART IV. VEGETABLE TAXONOMY. 



CHAPTER III.— THE THALLOPHYTA (Continued). 



Class I. — The Mvxomycetes, or Slime-Moulds. 



These are anomalous plants, so near the border-line between 

 the animal and vegetable sub-kingdoms, that some have regarded 

 them as belonging to the one, and some to the other. Naturalists 

 are not even yet fully agreed as to where they belong, but the 

 preponderance of evidence is in favor of regarding them as 

 plants. They are, however, so anomalous in their characters — 

 so different from other plants, — that it is deemed best to put them 

 in a class by themselves. They are not uncommon plants, form- 

 ing slimy masses amid decaying organic matters ; by far the 

 great majority are saprophytes, while a few, as the curious one 

 that causes the disease <? d c b a 



called "Club-root" on 

 the Cabbage plant, are 

 parasitic. During their 

 vegetative life they 

 avoid the light, and 

 creep about amoeba- 

 like among the organic 

 debris on which they 

 feed, but they produce 

 their fructifying organs 

 on the surface. These 

 are sometimes of con- 

 siderable size, occa- 

 sionally even as large 

 as a man's closed fist. 

 They vary, however, 

 in size and shape according to the species. When the fructi- 

 fication is ripe, it bursts, and very numerous thick-coated spores 

 are discharged, commonly leaving behind a kind of frame-work 

 which, being usually composed of capillary threads, is called 



Fig. 466. — Some of the different stages in the develop- 

 ment of Physarum album, one of the Myxomycetes. a, 

 spore; b, protoplasm escaping from spore; c, the same 

 when free from the enclosing membrane : ti, and e. after a 

 cilium has been acquired ; ./and g. after loss of cilium ; h, 

 i, k, I, coalescence of amoeboid bodies: m, a small Plasmo- 

 dium resulting from the coalescence of many amoeboid 

 bodies. After Cienowski, from L>e Bary's " Mycetozoa." 



