38 MORPHOLOGY AND CULTURE OF MICROORGANISMS 



Since within these groups various accessory types of fruiting occur, so 

 that some species show three or even more forms of spores, that type 

 of spore formation which is regarded as characteristic of the group is 

 known as the perfect stage. If sexual fruits are found, these constitute 

 the perfect stage of the group; if no such fruit is found, the most 

 characteristic asexual form is used. 



Between the typical forms are many gradations resulting in many 

 families whose relationship to one or the other group is difficult to 

 determine. Probably the ancestral history (phylogeny) of the fungi, 

 if known, would show several or many lines of descent rather than one. 

 Many thousands of species of fungi have been described, principally 

 in Latin, German, French and English. The literature is widely 

 scattered in monographs, reports and journals published in various 

 languages. For the purposes of the bacteriological worker, a few 

 representative groups with some of the significant species will be 

 considered here. 



BACTERIA. In the scheme of plant grouping presented (page 13), 

 which is only one of many attempts to show relationships, the bacteria 

 are placed with a group of single-celled green or blue-green forms as 

 Schizophyta or fission-plants because of reproduction only by the divi- 

 sion of the cells. Recent work of Lohnis, Cort and others have opened 

 possibilities of specialized spore-production in the bacteria. Such 

 reproductive bodies, if proved present and fully described, would 

 probably furnish a sound basis for a scheme of relationships of the 

 bacteria. At present it is undecided whether they are specialized 

 from higher forms by suppression of characters or represent a primitive 

 morphology with highly specialized physiological relations. 



PHYCOMYCETES. The Phy corny cetes are called algal fungi because 

 they resemble certain groups of green filamentous forms in many 

 particulars. In this group two general types of sexual reproduction 

 appear zygospore formation and oospore formation. The first, 

 found in the Zygomycetes represented by the common mucors, consists 

 of the fusion of terminal cells of branches of the mycelium similar in 

 appearance but differentiated in sex. As a result of this fertilization 

 large thick-walled resting cells are produced, called zygospores, from a 

 Greek root meaning yoked (Fig. 33). In oospore formation, found 

 in the Oomy cetes, the conjugating cells differ in appearance as well as 

 in function. The oospore or egg-cell is large and is rich in food 



