36 



TAXONOMY 



paratrophic, that is, are able to exist only upon living animals or plants. But 

 in spite of the many points of physiological similarity between fungi and 

 bacteria there are very wide morphological differences. In every fungus, be 

 it a mushroom, a morel, a mildew (Fig. 15, c), a smut-fungus, or an animal 

 parasite, like Herpes, we can always recognize two distinct parts, the mycelium 

 or vegetative section, and, arising from this, the spore-bearing or reproductive 

 section. The mycelium is in all fungi an irregularly felted mass of branched 

 filaments, the hyphae, which in many cases (e.g. Penicilliwm, Fig. 15, c) consist 

 of cylindrical cells set end to end, each cell having much the appearance of 

 a rod-shaped bacterium. The fructification is of varying degrees of com- 

 plexity, from isolated cells or chains of cells (Fig. 15, c) among the lower fungi 



Fig. 15. Ay Oscillaria tenuis (one of the Cyanophyceae), fragment of filament ; ch^ hollow cylindrical chromato- 

 phore ; c, so-called central body, finely vacuolated protoplasm with deeply-staining granules t black). B, Polytoma 

 uvella x flagellate with two anterior cilia ■ v, contractile vacuole ; k, nucleus ; h, membrane, cell contents filled with 

 assimilation products (paramylum). c, Penicillium glaucum (true fungus, mycomycete), mycelium has arisen from 

 the conidium a ; on aerial hyphae brush-like fruits with chains of conidia. Magn. a 2250, b about 600, c (from 

 Brefeld) 120. 



up to the highly complex sporophores of the toadstools and mushrooms. 

 Upon a suitable soil the mycelium is able to vegetate for long periods, 

 continually producing new reproductive cells or fruits. Among the bacteria 

 such a differentiation is nowhere to be found. Their vegetative phase is 

 either a single cell or a cell filament on which special reproductive organs 

 are not developed but which, like Cladothrix, breaks up entirely into 

 gonidia. When the reproductive organs, the spores, appear, the vegetative 

 cell as such ceases to exist. As in the myxomycetes and many other 

 protista, it is entirely used up in the formation of the reproductive cell. 

 The bacteria may therefore be termed holocarpoits, as contrasted with the 

 fungi which are eucarpous, that is to say, able to produce several successive 

 fructifications from the same vegetative thallus. 



Failing to find the kindred of the bacteria among the fungi we must 

 seek them among those low organisms which we have named collectively 



