ORDER PROTOMYCETALES 143 



developed hyphae show pronounced anisogamy in most cases. For the 

 latter reason the Monoblepharidales, Lagenidiales, Saprolegniales, and 

 Peronosporales were included in the subclass Oomyceteae of the Class 

 Phycomyceteae in the first edition of this book, following the practice of 

 Fitzpatrick (1930) and other mycologists. These were set apart from the 

 subclass Zygomyceteae, in which approximate isogamy was held to war- 

 rant such a distinction, accompanied as it was by loss of the power to 

 produce motile cells and by the greater predominance of chitin in the cell 

 walls. The fact that the simpler forms included in the Oomyceteae, such 

 as Chytridiales, and some of the Blastocladiales and Lagenidiales, show 

 isogamy and that many forms whose closest kinship seems to lie with 

 the Mucorales and Entomophthorales have pronounced anisogamy makes 

 it doubtful whether this character should be used to distinguish sub- 

 classes. Hence these two group names have been abandoned in this 

 edition. 



Order Protomycetales. As a very doubtful appendix to the Phyco- 

 myceteae so far considered must be added the Order Protomycetales, 

 with a single family Protomycetaceae. The true position of this group 

 among the fungi has long been the subject of speculation. The author 

 follows Fitzpatrick (1930) in placing these fungi among the Phyco- 

 myceteae but with very little idea as to what groups of that class may 

 have given rise to them. The most recent and extensive investigations 

 on the group are those of Sappin-Trouffy (1897) and of von Biiren (1915, 

 1922). The family seems to have no affinity to the Ascomyceteae or to 

 the other Higher Fungi, though it has been assigned to various positions 

 among these. It consists of one well-established genus, Protomyces, with 

 12 or more species to which 3 other genera have been added, Taphridium, 

 Volkartia, and Protomycopsis. Until life history studies are more complete, 

 the validity of their segregation is uncertain. All the well-known species 

 of these 4 genera are parasitic in the stems, leaves, or fruits of Ammiaceae 

 (Umbelhf erae) , Asteraceae (Compositae), and Cichoriaceae. 



A number of species have been described from various other families 

 but need further study before their validity is assured. 



The mycehum is subepidermal or intercellular in the underlying 

 tissues. It is septate at occasional intervals, each segment being pluri- 

 nucleate. The cell walls give a strong cellulose reaction with chloriodide 

 of zinc. Some of the segments of the mycelium enlarge and become 

 multinucleate (30-40 nuclei, in Protomyces inundatus Dang.). Within the 

 original wall the cell enlarges and becomes surrounded by a thick, three- 

 layered cellulose wall, the nuclei dividing several times to become 100-200 

 in number. These resting sporangia (or "chlamydospores" as some 

 authors call them) may remain in the tissues over winter or may ger- 

 minate the same season. In some species they are subepidermal and in 



