636 THE PHYLOGENY OF THE FUNGI 



agreement, regardless of the ideas as to the ancestry of the Ascomyceteae. 

 The author follows the school of Sachs in the belief that the evidence is 

 stronger in favor of the Floridean ancestry of the Ascomyceteae, but he 

 will attempt to indicate the viewpoints of this hypothesis which are most 

 unsatisfactory and to exhibit the evidence that convinced de Bary and 

 many of his successors that the Phycomyceteae actually gave rise to the 

 higher fungi. 



Among the points against the Floridean ancestry, the composition of 

 the cell wall has been emphasized. In the higher fungi as well as the lower 

 fungi the basic compounds making up the wall are various types of carbo- 

 hydrates, among which may be found cellulose, callose, various pectin 

 compounds, etc. Admixed with these, especially as the mycelium becomes 

 older, are various substances which, when in sufficiently large proportion, 

 prevent the reaction of the cell wall to the various cellulose tests, such as 

 chloriodide of zinc and certain stains and solvents. These admixtures are 

 sometimes fats, deposited in the surface layers of the wall, as is the case in 

 Monohlepharis, Blasiocladia, etc. In these, treatment with substances that 

 will saponify the fat (such as KOH solution, warm but not hot, followed 

 by thorough washing) will then permit the cellulose reaction to appear. 

 Far more often the hindering agent is a substance which, although it is 

 usually called chitin, has been shown to be sufficiently different from 

 animal chitin to warrant its designation as fungus chitin (see Chapter 1, 

 p. 3). This is found in some of the Chytridiales (e.g., Synchytrium) , to a 

 small extent in Phytophthora, but not enough to prevent the cellulose reac- 

 tion entirely, and in the Mucorales and Entomophthorales. Even in the 

 former it may not block the cellulose reaction in the younger hyphae but 

 usually does so in the more mature mycelium. The author's investigations 

 on Piloholus (1948) have shown that in P. kleinii van Tiegh. the cellulose 

 coloration by chloriodide of zinc is limited to the slightly thickened lip 

 surrounding the opening at the top of the subsporangial vesicle after the 

 sporangium has been discharged, while in P. longipcs van Tiegh. the lower 

 two-thirds or three-quarters of the sporangiophore and the trophocyst, 

 the basal swelling, and much of the vegetative mycelium show this reac- 

 tion. In the Entomophthorales the chitin appears to make up a large 

 portion of the cell wall but cellulose prevails in Basic/ iobolus (Couch, 

 1939). In the Ascomyceteae and other higher fungi, fungus chitin usually 

 blocks all cellulose tests although the presence of the latter may be shown 

 by chemical analysis. In the ascogenous hyphae of some lichens the cel- 

 lulose reaction shows up well. Some of the yeasts do not indicate the 

 presence of fungus chitin though cellulose seems to be replaced by other 

 carbohydrates. From the foregoing it seems that there is a growing trend 

 as we pass from the lower fungi to the higher fungi for an increased 

 amount of fungus chitin in proportion to the cellulose but in general the 



