252 ^ CENTURY OF PROGRESS IN THE NATURAL SCIENCES 



had the effect that it would seem to deserve, perhaps owing to the well-known 

 conservatism of systematists and their reluctance to make changes in the familiar 

 classification. 



So we find the monophyletic concept of the fungi strongly entrenched. To be 

 sure, the ideas of Sachs and a number of others (as pointed out by Vuillemin, 

 1912), that the fungi have arisen from algae at various points, still persist. The 

 most recent books to use the results of the recent cytological and anatomical 

 studies in the classification are the two books by Ernst Albert Gaumann (1926, 

 1949). 



In his later book Gaumann recognizes four classes of fungi. The first class 

 consists of the Archimycetes. They are endophytic parasites which, in their 

 early vegetative stages, are naked and, in some cases at least, amoeboid. Later, 

 the whole structure, often up to that stage still uninucleate, in spite of its 

 growth, forms a cell wall and then by multiplication of the nuclei and division 

 of the protoplasm becomes a zoosporangium or a gametangium, within which 

 are contained the motile naked zoospores or gametes. Of the four families recog- 

 nized two, Olpidiaceae and Sj'nchytriaceae, are usually placed in the Chytridiales, 

 because of the posteriorly attached single flagellum. The other two families, Plas- 

 modiophoraceae and Olpidiopsidaceae, have two anterior or lateral flagella and 

 are usually placed respectively near the Myeetozoa and the Saprolegniales. These 

 four divergent families are, according to Gaumann, probably to be assigned to 

 an origin among the Flagellata. 



Gaumann's second class, the Phycomycetes is acknowledged to be at least 

 diphyletic. The first three orders (Reihen), Chytridiales, Blastocladiales, and 

 Monoblepharidales are certainly related. Their zoospores (and motile gametes, 

 where formed) have a single posterior flagellum (which is of the whiplash type, 

 as in the first two families of the Archimycetes) , and the cell wall does not typi- 

 cally contain cellulose. They are derived from the Flagellata. The fourth Reihe, 

 the Oomycetes, has cellulose-containing walls and the motile cells, where formed, 

 have two anterior or lateral flagella, one of the tinsel type and one of the whip- 

 lash type. The vegetative structure is a more or less branched, coenocytie hypha 

 on which are formed rounded oogones, with one or more eggs (oospheres) which 

 are fertilized by conjugation tubes from antherids that arise nearby or at a dis- 

 tance and become attached to the oogone. The fertilized egg becomes a thick- 

 walled oospore. This Reihe is so similar in structure to the Siphoneae, especially 

 Vaucheria, that Gaumann seeks its ancestry in that general group, as did Sachs, 

 De Bary, and others. It has several families, soil or water inhabitants and strict 

 parasites in land plants. It ends blind, as the remainder of the fungi are not 

 considered to have derived from the Oomycetes. The fifth Reihe is that of the 

 Zygomycetes, from which the higher fungi are considered to have arisen. Vege- 

 tatively they resemble the Oomycetes, in that they are branched tubular coeno- 

 cytes, but their cell wall has chitin as its chief constituent. Sexual reproduction 

 is by the union of two nearly equal and similar gametangia to form a thick- 

 walled zygospore. Asexual reproduction is by the formation of sporangia, within 

 which are produced the encysted spores, instead of the naked zoospores of the 

 preceding class. These sporangia show great modifications, leading in several 

 directions to the production of wind-borne conidia (which in most cases repre- 

 sent indehiscent sporangia reduced in size, with contained spores reduced to one), 



