350 CLASS ASCOMYCETEAE 



Basidiomyceteae the cells are uninucleate, including the basidia, and 

 there is no nuclear fusion in the latter. This can be explained, according 

 to him, by loss of sexuality, as has happened in many of the Saccharo- 

 mycetales and other fungi, or by the occurrence of + and - strains which 

 in the absence of the reciprocal strain proceed to produce their basidio- 

 spores parthenogenetically. With the discovery of Itersonilia, with its 

 mycelium made up of dicaryon cells (as evinced by the clamp connec- 

 tions), and of Sporidioholus it seems that probably these are really much 

 reduced forms of Basidiomyceteae from either the Subclass Teliosporeae 

 or Subclass Heterosporeae, in both of which the teliospores often germi- 

 nate by repetition. 



The two families whose discussions follow are of very uncertain rela- 

 tionship. It is possible that the Spermophthoraceae are not far from the 

 Endomycetaceae. The Pericystaceae are of still more doubtful kinship. 

 Both need further investigation in order to confirm the validity of the 

 reported life histories and the conclusions drawn therefrom as to their 

 relationship. 



Family Spermophthoraceae. The only known species, Spermophthora 

 gossypii Ashby & Nowell, was determined to be the cause of the disease 

 called stigmatomycosis affecting the seeds of cotton (Gossypium) and 

 fruits of tomato {Ly coper sicon) in the West Indies. This was studied first 

 by Ashby and Nowell (1926) and further by GuilHermond (1928). The 

 germinating ascospores give rise to a nonseptate, coenocytic, dichoto- 

 mously branching mycelium with apical growth. The apices of the 

 branches may continue to grow while the older parts die and are cut off 

 by callose plugs as in some Phycomyceteae. No cellulose reaction is 

 shown upon treatment with chloriodide of zinc. Sometimes small cells 

 bud off from this mycelium and these may bud in turn, but it has not been 

 ascertained whether these are functional asexual spores. A short distance 

 back from the hyphal tips the mycelium forms spindle-shaped swellings, 

 the gametangia, which become separated from the usually short tip cells 

 by a cross wall, another septum setting this swelling off from the main 

 portion of the mycelium. The gametangia contain at first from four to ten 

 nuclei. These divide twice simultaneously and the resulting nuclei and 

 most of the cytoplasm form a dense axial strand surrounded by a vacuo- 

 late epiplasm. The axial portion divides into fusiform, uninucleate cells 

 which enlarge at the expense of the epiplasm. The rupture of the game- 

 tangium wall permits the nonmotile gametes to escape. Whenever two lie 

 in contact they unite by a conjugation tube within which, usually, the two 

 nuclei unite. From this conjugation tube there grows out a rather Hmited 

 branched septate mycelium of uninucleate cells. The ends of the hyphae 

 enlarge and are cut off by a septum and become spherical asci. The 

 nucleus divides three times and around each nucleus is formed a more or 



